SCR UYGULAMA ORNEKLERİ
Dimer devreleri
Silicon Controlled Rectifier Model Railroad Throttles
London Model Railroad Group SCR Throttle
The following is a schematic drawing of a Silicon Controlled Rectifier type throttle for use on larger scale model
railroads. Three versions of this throttle are shown on this page. They are not sophisticated designs but work well and
are tough and reliable.
Push Button SCR Throttle Schematic
It was designed for use on a "The London Model Railroad Group's" large O scale layout located at London, Ontario,
Canada. The prime requirements for the club throttles were that they be rugged, reliable and produce as little heat as
possible. Throttles of this type have been in service at the club since 1987 with excellent results. The throttle will
deliver 5 amps continuously and up to 18 volts DC. See Notes.
The Programmable Unijunction Transistor used to trigger the SCR is the key to this design as it ensures that the
SCR fires on every cycle of the fullwave DC. This gives a very efficient operation with low voltage loss and very little
heat generated. Please refer to your electronics books if you need more information on how the SCR and PUJT in the
circuit function.
The SCR throttle has momentum effect built in due to the memory provided by the 50uF capacitor at the PLUS input
of the OPAMP. There is no decay but this can be added by placing a 1 to 2 Megohm resistor in parallel with the 50uF
capacitor. Increasing the value of the memory capacitor will slow the action of the throttle controls.
Due to its unregulated voltage output, the SCR throttle will have a prototypical feel as trains will slow when climbing
grades and speed up when going down grades. The operator must work the throttle to keep their train from speeding
or slowing too much in hilly terrain.
SCR Throttle Setup Instructions
The 50K Trimmer is adjusted so that maximum output voltage can be obtained but keep the SCR triggering on each
cycle. To do this perform the following steps.
1. With no load connected to the throttle output and the AC input turned on.
2. Connect an analog voltmeter to the output of the throttle (0-30V).
3. Set the trimmer to its maximum resistance.
4. Press and hold the ACCELERATE push button until the output voltage stops increasing.
5. DECREASE the resistance of the trimmer until the output voltage peaks and then begins to fall again. When the
voltmeter needle starts to bounce slightly the SCR is at its maximum trigger angle. STOP.
6. INCREASE the resistance of the trimmer slightly until the meter needle stops bouncing. At this setting the throttle
will be able to deliver its maximum voltage. If the trimmer resistance is set too low the SCR will not trigger on every
cycle of the full wave DC at full output voltage and could be damaged by high current spikes.
Notes
* NOTE 1 At full throttle and with no load this circuit will deliver more than 25 volts. Therefore care must be taken with
auxiliary equipment and train lighting that may be connected to the track.
(Remember that most voltmeters only indicate average or RMS voltage and not the peak voltage which can be 1.4
times greater that the average.)
* NOTE 2 If your trains will run as fast as you need at lower track voltages than 18 volts then lower the input to 12 or
14 volts AC. The under load DC output voltage of this type of throttle is roughly equal to the RMS AC input voltage.
* NOTE 3 Add your own reversing switches to the output and a suitable circuit breaker for added protection if desired.
* NOTE 4 The use of good quality push buttons is a must as these are the most likely components of the throttle to fail
due to the heavy thumbs of some people.
Please feel free to use this design if you wish. It worked for our club it might be useful to you.
The following is a photograph of a typical SCR throttle installed at the London Model Railroad Group's layout. The
throttle has two reversing relays so that when the direction switch is in its centre position the throttle is disconnected
from the track. This is a club standard for all main line throttles.
The throttle boards are hung under the layout by hooks so that they could quickly be changed if a failure occurred.
This was a hold over from a previous throttle design that was trouble prone.
The power transformers were located in electrically safe enclosures to keep the weight of the throttle boards to a
minimum. Volt and Amp meters are connected at the terminal strip so that they are ahead of the relays.
Potentiometer Controlled Silicon Controlled Rectifier Throttle
The second schematic is a basic version of the SCR throttle circuit. It uses a potentiometer instead of push buttons
for control. All of the above set up instructions apply to this design as well except that the potentiometer is set to
maximum when adjusting the 50K trimmer.
Potentiometer Controlled SCR Throttle Schematic
The "MoAT" Project Throttle.
The third schematic is a throttle that was built for the London Model Railroad Group because of a quest for more
power (amps) to triple head an all brass 21 hopper coal drag with scratch built Steam locomotives.
A quest ranking somewhere between that for the Holy Grail and the Golden Fleece. The fact that the transformer (22
Volts and 15 Amps) that powers this throttle just happened to appear at the right time helped get it off the ground.
"MoAT" SCR Throttle Schematic
As the schematic shows this design uses two silicon controlled rectifiers that are triggered through a special SCR
trigger transformer. This transformer allows the cathodes and gates of the SCR's to be isolated from the control circuit
and thus permitting the incorporation of the over current protection into the throttle.
The SCR's form half of a rectifier bridge that provides the track power while the two diodes in the bridge module that
the SCR's replace supply power only to the PUJT and the control circuits. In effect the power flow through each SCR's
is halved because each is triggered on every other cycle of the full wave DC.
The current limiting simply bleeds the charge off of the memory capacitor if the voltage across the 0.05 ohm resistor
rises higher than the voltage at the plus input of Ic2. The voltage across this resistor is directly proportional to the
current through it (E = I X R). The level of limiting is adjusted by the 10K ohm potentiometer.
RED ROCK ENERGY
Beam Circuits. Conventions:
1. When light is applied to an LED the anode sources current and becomes positive.
2. Most of the LED Sensor circuits are not very sensitive to the power supply voltage, however some are. The
ones that specify a VCC of 5 volts have beam tested at that voltage. If a different voltage is used one should
verify operation and adjust the resistor components accordingly.
3. The higher the resistance in the circuitry providing current to the LED the better. I have specified and tested
using 22 MOhm resistors. 10 MOhm resistors will work almost as well and can be more easily obtained. I
have used 100 MOhm in some of these circuits which greatly improved sensitivity. However be cautious of
board and transistor leakage currents.
4. Almost any low leakage switching transistors can be used. I have mostly used BC337/BC327 transistors. The
generic 2N3904/2N3906 work just as well.
5. I use large 10 mm Lumex green LEDs with a clear case whenever possible, SSL-LX100133XGC. In my
testing this LED has been superior to most other LEDs used for light sensing applications. If you want to use a
smaller LED select high efficiency types. Select high Lumens per watt types. Don't look for just supper
brightness as this has more to do with optical geometry than efficiency.
6. All the circuits presented can be used in the complementary mode, i.e. swapping all component polarities and
swapping NPN for PNP types. An example of this is the beamstepper7 series driving the active low enables of
the 74AC240 gates. See below.
a
b
A
B
1. When LED1 is brightly lit it causes Q1 to ground
pin 3 of the gate. The voltage dropped by R2 is
sufficiently low enough to effect a low on pin 1 &
3.
2. With less light pin one rises above the threshold
and becomes high.
3. In darkness both inputs are high while pin 3
remains low.
4. This circuit is sensitive to the power supply
1. When LED1 is brightly lit it over powers the lessor lit
LED2 causing Q1 to ground pin 3 of the gate. The
voltage dropped by R2 is sufficiently low enough to
effect a low on pin 1 & 3.
2. When equally lit pin one rises above the threshold
and becomes high while pin 3 remains low.
3. When LED2 is more brightly lit LED2 absorbs the
current from LED1 which turns Q1 off and both
inputs are high.
voltage. The values given are for 5 volt
operation. For other voltages R2 & R3 will need
to be adjusted.
4. This circuit is sensitive to the power supply voltage.
The values given are for 5 volt operation. For other
voltages R2 & R3 will need to be adjusted.
h
g
G
H
1. This circuit is a pseudo SCR circuit to form a
Schmitt trigger that is normally ON. Unlike an
SCR this circuit can be switched off.
2. Assume LED1 is dark. Current will flow through
R3 & R1. This turns on Q2 which cusses current
to flow through R2, causing Q4 to turn on. This
causes the current flowing through R1 to
increase to a higher level latching the circuit
ON.
3. When sufficient light intensity is applied to LED1
it tends to absorb the current flowing through
R1. When sufficient current is absorbed Q2
turns OFF, causing Q4 to turn OFF. Current
flowing through R1 is reduced to a lower level
latching the circuit off as long as sufficient light
is applied to LED1.
4. The light intensity applied to LED1 must go
below a lower level to cause Q2 to turn back
ON.
1. This circuit is a pseudo SCR circuit to form a Schmitt
trigger that is normally OFF. Unlike an SCR this
circuit can be switched off.
2. Assume LED1 is dark. R3 prevents Q4 from turning
on. With no current flowing through R1 Q2 will also
stay off latching the circuit in the OFF condition.
3. When sufficient light intensity is applied to LED1 it
causes current to flow in the base of Q2 which
causes current to flow through R2. This current will
be greater than that which can be absorbed by R3
and the excess will turn Q4 ON causing current to
flow in R1. The sum of the currents from R1 and
LED1 is sufficient to keep the circuit latched in the
ON condition.
4. The light intensity applied to LED1 must go below a
lower level to cause Q2 to conduct less current.
When the current through R2 is insufficient to
overcome the current being absorbed by R3 Q4 will
turn OFF.
5. This circuit is sensitive to the power supply voltage.
The values given for a nominal 5 volts with a range
of about 2.5 to 7.5 volts. For other voltages R3 will
need to be adjusted.
c
C
d
D
1. When LED1 is brightly lit it sources current into
the base of Q1, out the emitter, and back
around through D2. Q1 being ON grounds R1.
Q2 being OFF raises R2 HIGH.
2. With the illumination on the LEDs about equal
both Q1 & Q2 will be OFF raising both R1 & R2
HIGH.
3. When LED2 is brightly lit it sources current into
the base of Q2, out the emitter, and back
around through D1. Q2 being ON grounds R2.
Q1 being OFF raises R1 HIGH.
4. At no time can both Q1 and Q2 be on at the
same time.
1. When LED1 is brightly lit it sources current into the
base of Q1. The current comes from R3. Q1 being
ON grounds R1. Q2 being OFF raises R4 HIGH.
2. With the illumination on the LEDs about equal both
Q1 & Q2 will be ON, due to base currents from R2 &
R3, pulling both R1 & R2 LOW.
3. When LED2 is brightly lit it sources current into the
base of Q2. The current comes from R2. Q2 being
ON grounds R4. Q1 being OFF raises R1 HIGH.
4. At no time can both Q1 and Q2 be off at the same
time.
f
e
E
F
1. This circuit is a pseudo SCR circuit to form a
Schmitt trigger that is normally ON. Unlike an
SCR this circuit can be switched off.
2. I will describe the left side operation, the right
side operates similarly.
3. Assume both LEDs are dark. Current will flow
through R2 & R5. This turns Q1 ON which
cusses current to flow through R1, causing Q3
to turn ON. This causes the current flowing
through R2 to increase to a higher level latching
the circuit ON. Both sides will be latched ON.
4. When sufficient light intensity is applied to the
LED2 it tends to absorb the current flowing
through R2 increasing the drive to Q2. When
sufficient current is absorbed Q1 turns OFF,
causing Q3 to turn OFF. Current flowing through
R2 is reduced to a lower level latching the circuit
OFF as long as greater light intensity is applied
to LED2.
5. When sufficient light intensity is applied to LED1
it overcomes the current absorbed by LED2 and
can supply current to turn Q1 ON. This in turn
causes Q3 to turn ON increasing the current
through R2 to a higher level latching the left side
ON.
6. This differential illumination of the LEDs has a
dead band where both sides can never be both
1. This circuit is a pseudo SCR circuit to form a Schmitt
trigger that is normally OFF. Unlike an SCR this
circuit can be switched off.
2. I will describe the left side operation, the right side
operates similarly.
3. Assume both LEDs are dark. R5 absorbs the current
through R1 sufficiently to starve the base of Q3
turning Q3 OFF. This turns Q1 OFF which reduces
current to flow through R1, causing Q3 to turn OFF
latching the circuit OFF. Both sides will be latched
OFF.
4. When sufficient light intensity is applied to the LED1
it tends to source current to the base of Q1 turning
Q1 ON. The current flowing in R1 is sufficient to
overcome the current absorbed by R5 causing Q3 to
turn ON which causes current to flow through R2
combined with that from LED1 bringing the base
drive of Q1 to a higher level latching the circuit ON
as long as sufficient light is applied to LED1.
5. When sufficient light intensity is applied to LED2 it
absorbs the current from LED1 and R1 starving Q1
of base drive switching Q1 OFF which in turn causes
Q3 to turn OFF latching the circuit OFF.
6. This differential illumination of the LEDs has a dead
band where both sides can never be both on.
7. This circuit is sensitive to the power supply voltage.
The values given for a nominal 5 volts with a range
off.
of about 2.5 to 7.5 volts. For other voltages R5 & R6
will need to be adjusted.
l
k
K
L
1. This circuit has greatly improved sensitivity in
low light conditions.
2. This circuit is a pseudo SCR circuit to form a
Schmitt trigger that is normally ON. Unlike an
SCR this circuit can be switched off.
3. Assume LED1 is dark. Q6 will not have any
base current nor collector current. Current will
flow through R3 & R1. This turns on Q2 which
cusses current to flow through R2, causing Q4
to turn on. This causes the current flowing
through R1 to increase to a higher level latching
the circuit ON.
4. When sufficient light intensity is applied to LED1
it sources current into the base of Q6 which
absorbs the current flowing through R1. When
sufficient current is absorbed Q2 turns OFF,
causing Q4 to turn OFF. Current flowing through
R1 is reduced to a lower level latching the circuit
off as long as sufficient light is applied to LED1.
5. The light intensity applied to LED1 must go
below a lower level to cause Q2 to turn back
ON.
i
1. This circuit has greatly improved sensitivity in low
light conditions.
2. This circuit is a pseudo SCR circuit to form a Schmitt
trigger that is normally ON. Unlike an SCR this
circuit can be switched off.
3. I will describe the left side operation, the right side
operates similarly.
4. Assume both LEDs are dark therefore Q5 & Q6 are
OFF. Current will flow through R2 & R5. This turns
Q1 ON which cusses current to flow through R1,
causing Q3 to turn ON. This causes the current
flowing through R2 to increase to a higher level
latching the circuit ON. Both sides will be latched
ON.
5. When sufficient light intensity is applied to the LED1
it sources current into the base of Q5, out the
emitter, and back through D2. Q3 absorbs the
current flowing through R2 decreasing the drive to
Q1. When sufficient current is absorbed Q1 turns
OFF, causing Q3 to turn OFF. Current flowing
through R2 is reduced to a lower level latching the
circuit OFF as long as greater light intensity is
applied to LED1.
6. When sufficient light intensity is applied to LED2 it
overcomes the current sourced by LED1 which
starves Q5 turning Q5 OFF and allows R2 to supply
current to turn Q1 ON. This in turn causes Q3 to turn
ON increasing the current through R2 to a higher
level latching the left side ON.
7. This differential illumination of the LEDs has a dead
band where both sides can never be both off.
j
I
J
1. R1 & R2form a voltage divider at 1/2 of the
supply.
2. When both LEDs are dark or illuminated equally
current can neither flow into Q1 nor Q2.
Especially since the two bases are connected
together resulting in Q3 & Q4 being both OFF.
3. With Greater illumination on LED1 current is
sourced into Q1 resulting in Q3 also being ON.
Q4 is also OFF.
4. With Greater illumination on LED2 current is
sourced into Q2 resulting in Q4 also being ON.
Q3 is also OFF.
5. At no time can Q3 or Q4 be on at the same
time.
1. R1 & R2form a voltage divider at 1/2 of the supply.
2. The top half operates essentially independent of the
lower half.
3. When LED1 is dark current from R1 flows into the
base of Q1 and through it's emitter into the lower
half circuitry. This cusses Q1 to be turned ON
resulting in Q3 being ON.
4. When LED1 is illuminated sufficiently to absorb the
current flowing through R1 Q1 is starved of base
current and is OFF causing Q3 to also be OFF.
5. When LED2 is dark current from R1 flows into the
base of Q2 and through it's emitter into the lower
half circuitry. This cusses Q2 to be turned ON
resulting in Q4 being ON.
6. When LED2 is illuminated sufficiently to absorb the
current flowing through R2 Q2 is starved of base
current and is OFF causing Q4 to also be OFF.
7. This is an interesting circuit in that it has 4 distinct
states as opposed to most of the other LED sensor
circuits having 2 or 3 distinct states.
3
Bipolar Stepper Motor Driver based on a CMOS 40106 Hex Schmitt Trigger Inverter.
Wilf's description.
The stepper controller operation is as follows (I think):
The LED photo detectors work together with Q1 and Q4 to enable either of the two independent oscillators. When the
LEDs are aligned with the sun, both LED sensors would be shaded by a "shadow mask", both Q1 and Q4 are on and
both
oscillators
are
disabled.
( Actually you don't need the shadow mask. Both transistors will be ON whether there is no light on the LEDs or both
LEDs have the same illumination. Either way they will have zero volts across the LED pair. Redrok. )
When one or the other LED is illuminated, the transistor is turned off and the oscillator is enabled and generates a
square wave.
The LED photo detector uses it's photovoltaic output voltage to drive the transistor base negative and the transistor
turns off.
Assume that LED1 is lit. LED1 anode voltage remains at +0.6V (clamped by the Q4 base-emitter) but the LED
generates a negative voltage at the cathode of -1V which drives the Q1 base negative and turns off Q1 collector
current. That releases the U1E input and the oscillator starts.
This is where the circuit gets funky: The outputs of the oscillators are connected to a "floating" RC network i.e. a
network that has no DC connection to the supply rails. External leakage currents can cause the DC level in such a
network to drift. Despite the lack of a DC reference, the average DC level of this network must hover near VCC/2 for it
to operate.
Measuring waveforms in this floating network with a scope probe can cause problems as the probe has a 1M or 10M
(x10 setting) impedance to GND.
I would recommend adding a high resistance voltage divider between VCC and GND with the midpoint connected to
the network to stabilize the DC level of the network to VCC/2 or better yet just below the lower trigger threshold
(approximately VCC/3)
Keeping in mind, the necessary floating DC level of the network, the AC coupled waveforms, superimposed on the DC
level will cross the thresholds of the Schmitt triggers as required.
The U1E oscillator output is capacitively coupled via C2 through R3 to the input of U1D. The signal will be clamped by
the input protection network to VCC+.6V. The output of U1D will follow the input without delay. The coupled signal
from C2 also drives an integrating RC network formed by R4 and C4. This causes a delayed signal of VCC/2
superimposed on the DC to appear at the input of U1C. Since the normal positive switching threshold of the Schmitt
trigger
is
3V.
See
the
spec:
40106
This VCC/2 signal by itself is not high enough to trigger the input of U1C. However with the added DC level, the signal
crosses the threshold of U1C causing a delayed negative output pulse at the output of U1C.
When the U1E oscillator output goes negative, the signal is coupled to the U1D output without delay and through R4
and delayed by C4 the signal appears at the output of U1C.
The result is a quadrature phase relationship between the signals on U1D and U1C with the U1C output delayed.
Now look at the output circuit (quite weird in the best BEAM tradition). When the oscillators are disabled the outputs of
U1C and U1D are both at VCC and the capacitor C1 is charged through Q2 and Q5 via the stepper coils to VCC.
Each output is buffered with a voltage follower half bridge power stage.
When the outputs of U1C and U1D are pulsing, the average value of the voltage on C1 is VCC/2 as the cap is
alternately partially charged and partially discharged through the stepper coils. The result is a bipolar current
waveform through each coil in quadrature that steps the motor in one direction.
The action is the same for the case of LED2 illuminated except that the delayed quadrature signal will be on U1D and
the motor steps in the reverse direction.
4a
Fully fleshed out Solar tracker based on the 40106.
This is the complete circuit. It is designed to drive TV antenna rotators which operate in a similar manor to a stepper
motor. In this case the motor is a capacitor run motor. The circuit provides the 90 degree quadrature drive for
reversing motion. Vdd should be be about 30 to 40 volts.
The sensor is the high sensitivity High sensitivity pseudo SCR sensor. Steering diodes are added to isolate the
several functions. Note the capacitor C10 to prevent or dampen mechanical oscillations.
Limit switches are added to limit extended movement.
A pulse oscillator is added to slow down mechanical movement. The movement is accomplished by delivering about 4
phase shifted cycles to the motor every 10 seconds or so. A manual Fast switch allows quick movements.
The level shifter is used to drive the power MOSFETs which deliver about 3 amps to the motor. An under voltage
protection circuit prevents damage to the upper MOSFETs if Vdd gets below about 15 volts.
5 volts Vcc is regulated from Vdd.
7e2
Bipolar Stepper Motor Driver based on a Dual Quad Buffer
Wilf and I have been developing another solar tracker that is based on a 74AC240 Dual Quad Tristate Buffer. There
have been a number of variations. These are the results.
The 74AC240 stepper driver works by enabling each half of the buffer. Only one half can be enabled at a time.
Let's assume that the top half of the driver is enabled. U1A & U1B along with R8, C1, & the input protection resistor
R7 form a square wave oscillator. The outputs of U1A & U1B directly drive one coil of a bipolar stepper motor.
U1C & U1D along with R9, C2, & the input protection resistor R10 form a 90 degree phase shift. The outputs of U1C &
U1D directly drive the other coil of the bipolar stepper motor. The motor turns in one direction.
If the second bottom half of the driver is enabled the oscillator using U1E & U1F work as before. U1H & U1G along
with R12, C3, & the input protection resistor R11 form a 90 degree phase shift. Except it's connected the other way
around from before so it's actually 270 degrees. The outputs of U1H & U1G directly drive the other coil of the bipolar
stepper motor. The motor turns in the other direction. Neat, Huh!
An earlier version of the circuit didn't work well because the the sensors presented an analog enable signal. This was
sometimes at the threshold voltage which caused the buffer to have high idle current and sometimes cross coupling
which was a bad thing. %^(
What was needed was a sensor that had a Schmitt trigger input. This could be done using a Schmitt trigger gate
which works well. I suggest a 40106 or 74AHCT14. However, this needs a second IC.
A better solution is to make the sensor have Schmitt action. The first version was:
Normaly OFF pseudo SCR sensor
The problem was that the pseudo SCR circuit worked over a limited voltage range.
Normaly ON pseudo SCR sensor
works better. Q1 & Q3 and Q2 & Q4 each form a bistable latch similar in operation to an SCR.
Let's start with the left side without the LEDs. Initially no current flows. The series resistors R5 & R2 cause a small
bias current to flow in the base of Q1, which reflects current through R1 causing Q3 to conduct. Since Q3 shorts out
R5 the current through R2 doubles. The output at the collector of Q1 snaps high disabling the connected buffers.
(Note, R5 & R6 aren't actually required. It turns out that leakage currents in the transistors is enough to get started. I
tried many transistors and never found one that didn't work as expected. Prudent circuit design demands that R5 & R6
be included because one might find a transistor that is so perfect it won't work. Bummer. )
The now connected and lit LED1 has the ability to absorb the current through R2 starving Q1 which switches off
resulting in the output snapping low. Q3 also switches off reducing the bias current in R2 to 1/2. This condition persists
until the LED goes dark.
You might ask where the current for the other side of the LED comes from. It is from base of Q2 on the right side.
Actually, when the left side is turned off the right side is turned on doubly as the current from both R2 and R3 go
through the base.
The right side works the same way. Since the LEDs are connected anti parallel only one latch can be off at a time.
This is safe for the buffers.
When both of the quad buffers are supposed to be off it is essential that all inputs not be near the threshold to have
the lowest idle current. R13 & R14 ensure that all inputs be near ground. All inputs are connected to R13 or R14 either
directly, through input resistors, or through the stepper motor windings. R13 & R14 can also be connected to VCC.
They don't even need to be to the same voltage, although it operates quicker if they are the same voltage.
I have tested this circuit with about 25 different 74AC240s. They all worked as expected.
I ran the circuit from about 2.4V to 8.5V. OK, one shouldn't go past 7V to be within the specs of the 74AC240. I even
have found some 74AC240s that worked to 14V, but I wouldn't recommend this.
The sensor section was tested to 40V. It still worked well, the sensitivity is less because the bias currents are
proportional to voltage which requires brighter illumination to work properly.
The step patterns are not perfectly symmetrical because this is essentially an analog circuit. Some resistor adjustment
may be needed.
To change the speed of the motor adjust the capacitor values. Note, all three need to be the same value.
I have chosen the time constants of R9-C2 & R12-C3 to be about 3/4ths of R8-C1. Try to keep these ratios. ( BTW,
I'm not sure this is the exact ratio but it seams about right. )
The 10M resistors in the sensor are the largest commonly available resistors in 1/8W size. I tried 22M in 1/4W and
that worked well with added sensitivity. I suppose if you could find 100M they would work even better. However be
careful of leakage currents on the board and transistors.
I have a variation which is even more sensitive to low light levels. See:
High sensitivity pseudo SCR sensor
7e1
Bipolar Stepper Motor Driver based on a Dual Quad Buffer
Optimized for circuit layout
This variation uses the same number of parts but has a better layout.
The description of operation is the same as the above circuit except the phase shifter is reversed and connected to a
single point on the oscillator.
This might have an application using a 74AC125 quad single mux where another oscillator may be present.
7e3
Bipolar Stepper Motor Driver based on a Dual Quad Buffer
My first attempt, note the neat circuit symmetry.
I added the an LED sensor to Wilf's Tri-Bridge.
I needed to drive the right side of the bridge with an inverted signal. This signal is not available on the left side. I
needed to add an inverter. The inverter has a 10K collector load resistor. This pulls up the right side when the left side
is low. When the left side goes hi the inverter transistor is turned on pulling the right side low.
The PSH H-Bridge circuit has a curious quirk. It doesn't work well when on input is pulled to a supply rail. The problem
is that the driver transistor can only saturate so much. This starves the output transistor of base current. The simple
solution is to have either an input resistor or limit the voltage with a diode as I did here.
Neat bridge. ledtri2
This works much better.
In the last version of this LED bridge the operation was limited to about 3.6V or higher. In this version I attempted to
make it work at a lower voltage with greatly improved sensitivity.
LED1 & LED2 along with Q11 & Q12 form a sensitive light to current amplifier. Only one of these transistors can be
ON at the same time. Let's assume LED1 is lit. Q12 supplies amplified LED current to Q10 then Q7 then to output
transistor Q3. In addition Q7 passes triply amplified LED current out it's emitter and into the emitter of Q6 which
transfers that current out Q6's collector and into the base of output transistor Q2. R1 & R2 form a voltage divider at
half of the supply. This assists in turning on Q6.
This circuit is essentially analog in nature. The current driven into the motor is proportional to the difference of the
current supplied by the LED pair. So when equally lit, or dark, the current goes to zero.
I found that the first version works well from 2.9V on up. To improve this I added D1 which extends operation down to
about 2.5V. Both of these versions have low idle currents primarily from R1 & R2.
By adding a second diode, D2, operation works down to about 1.9V. However, the idle current is higher. About 1mA at
1.9V to about 10mA at 5V.
The circuit is quite sensitive to ordinary room light in my lab, lit with fluorescent lights. Just orienting the plug board on
the table changes the motor from full forward to reverse. A slight wave of the hand has a dramatic effect. Very
sensitive.
AC motor speed controller kit - K2636
This kit was designed to control the speed of AC motors with carbon brushes, anything from drills to saws to vacuum
cleaners. Unlike other circuits such as normal dimmers the kit performs a phase cut only once per period. The
moment of cutting determines the speed, which can be adjusted from 5% to 95%.
The kit provides high torque even at low speeds. RFI is suppressed to eliminate noise and interference. The circuit
controls both low voltage (from 24VAC to 240VAC at 5.5A) AC motors and mains voltage (110VAC or 220VAC)
loads.
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The supply and load circuits are electrically isolated from each other for safety and reliability. The control circuit is
powered by the mains, but the load supply may be derived from a different AC source. Both voltages should be the
same frequency and the same phase or opposite phase.
Parts list:
 R13: 27 ohm resistor
 T4: BC517 transistor
R1: 4.7K resistor
 R14: 390K resistor
 TRI1: BT137F-600 Triac
R2: 3.3K resistor
 RV1, RV2: 100K trim potentiometers
 F1: 250mA slow fuse
R3: 680 ohm resistor
 C1: 470uF electrolytic capacitor
 F2: 5A slow fuse
R4, R5: 22K resistors
 C2: 1uF electrolytic capacitor
 L1: 50uH/1kHz coil
R6: 1.5K resistor
 C3: 100nF capacitor
 Trafo1: 2x6V/1x0.3A
R7: 47K (50Hz), 10K (60Hz)
 C5: 47nF capacitor
 Heatsink for the triac
R8: 100K resistor
 terminal blocks (VAC, load and
 C6: 100nF/400V capacitor
mains)
R9: 100 ohm resistor
 C7: 47nF/400V capacitor
 J1, J2 mains voltage jumpers
R10: 120 ohm resistor
 D1, D2, D7: 1N4007 diodes
printed circuit board
R11: 68 ohm resistor
 D3-D6: 1N4148 diodes
R12: 1K resistor
 T1-T3: BC547B transistors
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Sun light control automatically using SCR
This circuit controls the turn the power off consumption in home automation. If it is daytime working to break the
circuit. But at night is connected to a working electrical AC 220 volts. Such as the opening and closing of the bulb.
This lamp will illuminate when the light bulb goes off into the evening and on beginning to dawn.
How
circuit
works
The circuits ready working. When the male plug, or for the circuit to the AC line power at 220 volts. The plug socket is
connected to appliances in the home. Or connect with bulbs. The circuit is based on the brightness of the light incident
on the LDR. By the features is as follows.
When LDR received an indirect light. It will have a low resistance causes a current flow through too much or through
to a ground fully. Makes a capacitor C1 look like short circuit. As a result, the transistors Q1 and Q2 not works. So not
have a voltage pulse to trigger a SCR1(T106) or stop working so as to short-circuit the AC power. Makes electrical
components, or lamps connected to the plug socket. Or the connector points SK1. Therefore not working or notice a
light bulb goes out.
But when the LDR is received the sun light. The it ‘s body will has the high resistance. Makes the current flowing
through the less. So flow to store at the C1. So have a voltage across it to use as the bias voltage to the transistors
Q2(BC337) and Q1(BC327) runs. So has the voltage pulse to trigger to provide the SCR1 also works. Therefore
virtual circuits is connected to the AC power. Makes the electrical components or the lamp that connected with the
plug socket or the point-SK1 or noticed the lamp is lit.
Additional, the LDR stands for the Light Dependent Resistor. Acts as a general sensor light. It is a type of resistor
whose resistance value changes according to the intensity of incident light transmitted to it. If there is much light, the
resistance is low, (as a result of the current through a lot). If low light, the resistance is high, (as a result, less current
flow). The sensitivity of the circuit will adjust the variable resistor VR1.
Electrical appliances or light bulbs that are connected to a plug socket or points combination with SK1 about not
exceed 200 watts. Which depends on the tolerance power of diode D1, D4 or D2, D3 and SCR1. When working AC
circuits to flow seamlessly through these devices, particularly the diode number 1N4007 will allow current to flow only
up to about 1 amp.
Do not install the LDR to the direct exposure to the light from the lamp will turn on-off. Provides been specialized the
normal bright light only. Or the the back lamps, the light from the light bulbs.
Mini Emergency Lighting
This mini emergency lighting are used to automatically give lighting when ac line power go out. Which they consist of
one lamps, a battery, and a low voltage sensor. This projects design take advantaged of simple circuit techniques and
cheap.
Special feature:
1. Small-sized : output with 2.4V 5W lamp and 3V battery.
2. No transformer so Lightweight and easy to build.
3. No relay so be Silent and small.
4. etc.
How it works.
To begin with we use 4-5V dc power supply that without transformer. Next, the AC 220V input to passed trough R1 to
cut current down and D1 to rectifier AC to DC in half wave type. Then, the dc pulse or fluctuating signal is smoothed
with C1-capacitor. Which has voltage dropped across of 4.5Vdc
And then SW1 is used to turn on-off the next circuit as sensor,control,battery charger and lamp circuit. First of all, in
normally power the lamp go out not light since current pass to R4 to base of Q1 cause it is bias so high current flow
through D2-diode,R5-resistor to collector-emitter of Q1. Thus not has current bias to base of Q2,Q3 ( Darlington
transistor) cause they not conduct current, so not has current pass Lamp, it so not light.
Note: However, this circuit is not suitable for practical applications. Because of the small size and short
duration.Cheap emergency lights using D313 •
And later the power AC line go out, So not has current through S1, and then current from 3V battery not current
through D2 be due to diode not allow current as , is a one-way street. It will not work if you put it in backward. And
making Q1 does not work.
But this battery current will flow to R5 through base Q2,Q3 they so is bias current is result of high current flow to Lamp
glow light up at once.
Friends can use Nicad Battery or NiMH battery the size is 1.2V x 2 give the light has just enough. This circuit can
charge automatically batterys.
How to builds
This circuit is easy you so can build them with yourself on universal PCB board.
The detail components
Q1,Q2,Q3______C9014,C9013___1A
50V__NPN transistor
D1____________1N4148 75V 150mA Diodes
D2_______________1N4004 400V 1A Diodes
L1_______________2.4V 5W Lamp
L2_______________Neon Lamp
S1______________Slider Switch
C1______________ 47µF 50V Electrolytic
Capacitors
R1______________220K___1/2W resistors
R2______________33K___1W resistors
R3______________10K___1/2W resistors
R4______________1K____1/2W resistors
R5______________15K___1/2W resistors
B1______________3V battery (AA 1.2V)
18 LED dimmable LED lamp by LM2941C
This circuit is a dimmable white LED lamparray with 18 LED Display.
The lamp brightness is regulated as long as the input voltage is above 10.5V. A low-dropout analog voltage regulator
is used for a simple and relatively efficient design. The lamp produces enough light to use as a a reading lamp or a
small work lamp.
Read More Source: http://www.solorb.com/elect/solarcirc/18ledlit/index.html
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Bike tail LED light flashing
This is a bike tail LED light flashing as the planet Bike Blinky Safety. When we use the bicycle(normal bike) at night.
we used IC1 IC555 Oscillator signal is output to a lot LED super bright.
Present roads in good condition than the former roads, the traffic is convenient. But often car ran high speeds. When
we use the bicycle(normal bike) at night. Although we will attach the reflective sheeting at the end of the bicycle. But it
could be dangerous. We should attack the planet Bike Blinky Safety at the end of our bike would be better.
Operation of the circuit we used IC1 NE555 Oscillator signal is output at pin 3 of IC1, which frequency can be
determined by R1, R2, C1 and output voltage to a current flowing into pin B of Q2. Q2 makes LED1-LED10 will light
work. However, if the output signal voltage is 0 volts, Q1 will work,The Q2 stopped LED11-LED20 are bright.When a
high voltage again.
We may use battery AAx4 (1.5V x 4 = 6 Volts) Makes can use long time than 3 month when 3 hour everyday. Or we
can AC dynamo as power supply source. It is good ideal for save money buy battery and reduce Chemical waste. but
must have DC regulate as well.
Value of resistor R controls duration of time delay provided by RCA 40841 dual-gate FET in SCR trigger circuit, with
SCR in tum serving to triggertriacfor handling highcurrent resistive or inductive AC loads. Maximum delay of 5 min is
obtained when R is 60 megohms (IRC type CGH or equivalent resistor). Timing is accurate within 10% over
temperature rangeof -25℃to +60℃. D3 should be rated 60 V Use any SCR capable of handling triactrigger
current,rated 60 V.- Linear Integrated Circuitsand MOS/FET,s, RCA Solid State Division,Somerville,NJ,1977,p435437.
Battery charger circuit using SCR.
Simple battery charger based on SCR is shown here.Here the SCR rectifies the AC mains voltage to charge the
battery.When the battery connected to the charger gets discharged the battery voltage gets dropped.This inhibits the
forward biasing voltage from reaching the base of the transistor Q1 through R4 and D2.This switches off the
transistor.When the transistor is turned OFF,the gate of SCR (H1) gets the triggering voltage via R1 & D3.This makes
the SCR to conduct and it starts to rectify the AC input voltage.The rectified voltage is given to the battery through the
resistor R6(5W).This starts charging of the battery.
When the battery is completely charged the base of Q1 gets the forward bias signal through the voltage divider circuit
made of R3,R4,R5 and D2.This turns the transistor ON.When the Q1 is turned ON the trigger voltage at the gate of
SCR is cut off and the SCR is turned OFF.In this condition a very small amount of charge reaches the battery via R2
and D4 for trickle charging.Since the charging voltage is only half wave rectified ,this type of charger is suitable only
for slow charging.For fast charging full wave rectified charging voltage is needed.
Circuit diagram with Parts list.
AC Dimmer for Lamp 6.3V
This the circuit AC dimmer low voltage For lamp 6V. While this friends may don’t see the advantage of this circuit. But
I thinks first step advantage be something get learn the work of Triac. And have tall safety , because of use AC Low
Voltage. Which the work is simple be The UJT Q1 will do the frequency give Triac work or make Lamp the bright. By
have work rate of Triac can control with R1 or Be something dimmer there. You will may apply with the size Voltage
the other all right. The Q1 use UJT – 2N4891 or other. A friend may gain an advantage from AC Dimmer for Lamp 6V
, please sir.
AC lights dimmer with triac
This circuit has can to turn down a light bulb arrives at 100W. If Triac there is tall temperature should hold Heat Sink or
let off the heat. The Diac be diode that perform be formed encourage or Trigger Diode 2 kinds are way or
Bidirectional. The VR1 use for fine decorate turning down fire. Caution this circuit must is in a box closes all the time
that have the electricity flows through.
In figure 2 well than the first circuit
Operation of the circuit be Lamp L1 is adjusted by adjusting the light of VR1. This will serve to control the speed of
charging of C1, Because triac will work. When C1 has charged to the voltage at the triac work.When adjusting the
VR1 C1 will charge as little faster lamp is lit.If the adjustment of VR1 C1 will charge very slowly.The little light bulb.
Because the triac does not work over the triac during the work.The light bulb will dim down by adjusting VR1.The R1 is
placed for protection VR1 prevent damage.The R2, C2 is used to eliminate signal disturbance. Both produced and
external circuit.
1200 Watt AC Dimmer by Triac Q4006LT
This is Power AC Dimmer 1200 watt size. It is use a triac Q4006LT. Friends ever tour is the foreign land has and to
ever reach rest a hotel. On bed head has will head bed fire decorates. It has a button opens-close and a button
controls the brightness with the equipment this/these be AC Dimmer follow our circuit can fine to decorate.
The VR1 for control the light besides when friends apply TRUE work. The Q1 -Q4006LT , should hold heat sink with
and should be careful specially prohibit catch one ( part ) which part in the circuit , because read will bump against the
electricity can suck. I hopes this circuit , friends can induce apply be AC Dimmer with electric other appliances bump
against emphasize kind coil heat equipment , be lucky please yes.
Typical home light dimmer uses a TRIAC
Triacs cannot control the high current values that SCRs can
Here is the actual view of the circuit above. Note the inductor and the capacitor are used for phase shifting and
noise filtering. Have you ever noticed the 60 Hz ringing sound that comes from light dimmers and sometimes the
filament of incandescent lights that are dimmer controlled? It is the result of the chopping of the sine wave feeding
the light.
The fan is trying to keep the environment cool (CPU, industrial process, engine) The Fan Speed Control circuit uses
2 thermistors as a voltage divider to control control the TRIAC trigger circuit. The fan speed is thus proportional to
the temperature.
Here a low voltage logic circuit is used to control a higher voltage
An Optocoupler is used to keep the low voltage circuit safe from the higher voltage.
AC
load
(heater
motor).
DC motor controller diagram with SCR and cmos ic
This is speed controller circuit of 12Volt DC motor.You can adjust the speed of rotation of the spindle motor from 5-60
cycles per minute. The work of circuit, The IC1 is nand gate ic type,It accepts the voltage from the bridge diode BD1.
But there is no filter to smooth current.The other in the pin 2.The VR1, C1 and R1 is a phase shift or time delay to slow
down,voltage from pin 3 to triggers pin the gate of SCR1 to work.Or conductors to the motor, causing it to rotate.
Speed of the motor, can be achieved by adjusting VR1.
The power supply input pin 14 of IC1 is filtered to smooth the current, by through D2 and C2. The D1 prevents the
noise from the motor. and D3 is reverse-voltage protection of motors. This can cause circuit damage. If the circuit is
used with a motor that consumes more power. Heat sink should be attached to BD1, D1 and SCR1, because heat up.
May cause equipment damage.