1. Scratch Robots Motor Controller

2. Tools Radio Shack Tools $ 9.00 – Test Jumpers $ 3.00 – Screw driver $ 7.00 – Wire Strippers $ 20.00 – Multimeter -------------------------- $39.00 - Total Scratch Robots www.build-it-yourself.com Motor Controller Tools

3. Scratch Robots www.build-it-yourself.com 3-state Motor Controller 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 $ 3.00SN754410 Quadruple Half-H Driver Geared Motor hobbyengineering.com/H2028.html $10.00Several Tamiya options $40.00 Total Parts Motor Controller Circuit Board pictures

4. Scratch Robots www.build-it-yourself.com 3-state Motor Controller +9V R1 Photo resistor 2K light 50K dark R2 10K R3 R4 7 8,16 4,5,12,13 21 3 6 R5 10K 5V to 9V DC Motor 1A D1 1A 30V D4 D2 D3

5. Scratch Robots www.build-it-yourself.com 3-state Motor Controller Truth Table: Light Sensor R1BlackWhiteBlackWhite Light Sensor R2BlackBlackWhiteWhite Motor StateOffRightLeftOff Wish List: 1)Make a printed circuit and solder parts 2)Add clockwise, counter clockwise lamp 3)Add on/off lamp 4)Add on/off switch 5)Research geared motors and shaft accessories

6. 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 Motor Controller Circuit Board When the light sensor sees black, the motor is OFF. When the light sensor sees white, the motor is ON www.build-it-yourself.com Scratch Robots On/Off MOSFET Motor Controller

7. +6V to 9V S DG 5V to 9V DC Motor 1A R1 Photo resistor 2K Ohms light (on) 50K Ohms dark (off) R2 10K Scratch Robots www.build-it-yourself.com V Gate On/Off MOSFET Motor Controller

8. Q1 IRF510 N-channel MOSFET 2V-4V GS trigger voltage 20V GS Max voltage 4A DS current G – Gate D – Drain S – Source Radio Shack Breadboard MOSFET On/Off Controller Build-It-Yourself +6V to 9V S DG 5V to 9V DC Motor 1A R1 Photo resistor 2K Ohms light (on) 50K Ohms dark (off) R2 10K If the voltage between the Gate and Source, V Gate, of this N-channel MOSFET 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 4 volts. Then the motor will run. www.build-it-yourself.com Scratch Robots V Gate On/Off MOSFET Motor Controller

9. www.build-it-yourself.com R2 Variable Resistor 9V R1 Photo Resistor V Gate V Gate 9V 10K 4K(light)+10K V Gate = 6.4V = V Gate 9V R2 R1+R2 = V Gate 9V 10K 16K(dark)+10K V Gate = 3.4V = Voltage Divider (FET Gate Bias Control) Scratch Robots MOSFET Motor Controller

10. Test NO.Min R (K Ohm) Max R (K Ohm) Medium R, Gray (K Ohm) 164212 23308 364211 43.7247.4 52020050 676018 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 Standard Radio Shack Light Sensor package of 6. Min ohms - WhiteMed ohms - GreyMax ohms - Black