Introduction: SERVO DRIVER / TESTER (IC4001)

SERVO DRIVER (one axes real time position)

This is a circuit made long time ago but serve me well with no problems at all.
The circuit here it's been used to rotate a mini camera which have been placed into a plexiglass enclosure for waterproofing purposes.

It can be used for 90/180 degrees and continuous rotation servo as well.
Components are not critical and can be found all over the internet or from a local store.
The circuit can drive nano, micro and large servo (1) up to 1000mA consumption.
Never the less there are 2 choices of components depending on what you are going to drive.


On the components picture chart:
On the left are all the components needed for nano, micro servo.
On the right are the components needed to be replaced for standard / large servo.
In such event it is best to apply a heatsink to T1 transistor.

The SW1 switch is optional, it's purpose is to “cut” the circuit from the servo so it can turn freely in case of any maintenance, cleaning or that ever else you can think off while the circuit is ON.
The PCB must be 67mm horizontal x 50mm vertical.

P1 = 220K
P2 = 47K
P3 = 100K


Connect the servo to out put. Pay attention at this point as there are 3 wires. One is for positive (+) and usually will be in white or red color, one for negative (-) black and an other one usually in yellow color for the servo operation (e).
Connect the circuit to 15-12VDC power supply.
The LM7809 will provide the 9V required for the circuit OR you can use a 9VDC supply directly (see the diagram).
P1=220k sets the servo end points.
P2=47k sets the servo neutral point. Adjust it that way so when the servo is been set to any position it will stay locked to that point.
P3=100K serves as the servo positioner.
Have fun :)



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    12 Discussions

    Please provide circuit diagram. I could not locate. anywhere.

    Some people with an electronics background would find your Instructable more interesting and understandable if it had included a schematic - as the usual custom...

    2 replies

    Agree, but as i said above this is an old project. Unfortunately i have lost the schematic. All is needed after all is the print the pcb for this to make it work.

    Some people with an electronics background would be inclined to build and test your circuit on a protoboard before they committed to printing a pcb, most especially if they were building your project for learning rather than creating a usable device. And even if one were building your project as some kind of usable device, they might use something different than a pcb. While it is true that some readers might be able to "derive" a schematic from your Instructable, you would probably be the best person to derive and publish this. Perhaps you will provide a schematic for the next Instructable you offer...

    Thank you for this nice tutorial :). In the case of standard/large servo what should be the orientation of D2 ?

    2 replies

    I want to use this circuit to build a numberplate flipper for a car. Is there a way to connect an on/of switch which one can flip to get a preset start and stop point. Eg when on it will go to 90 degrees and when off it will go to 0?

    1 reply

    No, not on this circuit. There is a swich (SW1) that disconnects the servo from the circuit for free handed rotation.

    Hello smithedwin,

    P1 = 220K, P2 = 47K, P3 = 100K. Nice to know you are going to make it!