Scratch Robots
Motor Controller
Scratch Robots
Motor Controller Tools
Tools
Radio Shack Tools
$ 9.00 – Test Jumpers
$ 3.00 – Screw driver
$ 7.00 – Wire Strippers
$ 20.00 – Multimeter
-------------------------$39.00 - Total
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3-state Motor Controller
Motor
Controller
Circuit
Board
pictures
Radio Shack Parts
$ 9.00 – 1-1/8” Modular IC Breadboard
$ 3.00 - Photo Resistors
$ 3.00 - 22 Gauge Hookup Wire
$ 3.00 - 10K Potentiometer x2
$ 3.00 - 9V connector
$ 4.00 – 1A, 30V diode x 4
$ 2.50 - 9V battery
-------------------------$27.00 – Sub Total
Pololu Part
pololu.com/catalog/product/24
$ 3.00 SN754410
Quadruple Half-H Driver
Geared Motor
hobbyengineering.com/H2028.html
$10.00 Several Tamiya options
$40.00 Total Parts
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Scratch Robots
3-state Motor Controller
R1
Photo resistor
2K light
50K dark
+9V
8,16
R5
10K
2
R2
10K
1
D1
1A
30V
D2
3
R3
7
R4
5V to 9V
DC Motor
1A
6
D3
4,5,12,13
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D4
Scratch Robots
3-state Motor Controller
Truth Table:
Light Sensor R1
Light Sensor R2
Black
Black
White
Black
Black
White
White
White
Motor State
Off
Right
Left
Off
Wish List:
1)
2)
3)
4)
5)
Make a printed circuit and solder parts
Add clockwise, counter clockwise lamp
Add on/off lamp
Add on/off switch
Research geared motors and shaft accessories
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On/Off MOSFET Motor Controller
Motor
Controller
Circuit
Board
When the light sensor sees black,
the motor is OFF.
When the light sensor sees white,
the motor is ON
Radio Shack Parts
$ 9.00 – 1-1/8” Modular IC Breadboard
$ 2.00 - IRF510 N-channel MOSFET
$ 3.00 - Photo Resistors
$ 3.00 - 22 Gauge Hookup Wire
$ 1.50 - 10K Potentiometer
$ 3.00 - 9V connector
$ 2.50 - 9V battery
-------------------------$24.00 - Total
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Scratch Robots
On/Off MOSFET Motor Controller
+6V to 9V
R1
Photo resistor
2K Ohms light (on)
50K Ohms dark (off)
R2
10K
5V to 9V DC Motor
1A
VGate
G
D
S
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Scratch Robots
On/Off MOSFET Motor Controller
R1
Photo resistor
2K Ohms light (on)
50K Ohms dark (off)
R2
10K
+6V to 9V
5V to 9V DC Motor
1A
VGate
G
D
S
Q1
IRF510 N-channel MOSFET
2V-4V GS trigger voltage
20V GS Max voltage
4A DS current
G – Gate
D – Drain
S – Source
If the voltage between the Gate and Source, VGate, of this N-channel
MOSFET is < 2 volts, no current can flow between the Drain and
Source terminals. The motor will not run. If the Gate to Source
voltage is > 4 volts, then current will flow between the Drain and
Source and the motor will run.
Adjust R2 so motor is off when R1 sees no light. The Gate voltage
should be < 2 volts. When R1 sees light, its resistance should
decrease raising the Gate voltage > 4 volts. Then the motor will run.
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Radio Shack
Breadboard
MOSFET
On/Off Controller
Build-It-Yourself
Scratch Robots
MOSFET Motor Controller
Voltage Divider (FET Gate Bias Control)
9V
VGate
9V
R2 = R1+R2
VGate =
9V
10K
4K(light)+10K
R1
Photo Resistor
VGate
VGate = 6.4V
R2
Variable Resistor
VGate =
9V
10K
16K(dark)+10K
VGate = 3.4V
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Standard Radio Shack Light Sensor package of 6.
Min ohms - White
Med ohms - Grey
Max ohms - Black
Test NO.
Min R
(K Ohm)
Max R
(K Ohm)
Medium R,
Gray (K Ohm)
1
6
42
12
2
3
30
8
3
6
42
11
4
3.7
24
7.4
5
20
200
50
6
7
60
18
The Problem: In a package of 6 light sensors, the resistance varies significantly.
Note: Test No. 1, 3, 6 have the same physical size.
Their resistance ranges are closer to each other than to other three.
For 1, 3 and 6, the thresholds may be set, i.e. to 10 K Ohm and 25 k Ohm.
Updated 10/05/2010