Simple Servo Controller

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Servo motors have many uses in everything from robotics to puppetry to photography and beyond. These little motors can position their output shaft to any position on command and hold that position. Most servos have a range of motion to about 210 degrees and thankfully are very easy to control with a simple circuit such as the one presented here. Using just a 555 timer and a few support components this circuit can control a servo through it's full rotation based on the position of a pot. This circuit was originally published in the Think Tank column of the October 1995 issue of Popular Electronics.


Schematic for the servo controller


Total Qty.
R11820 Ohm 1/4W Resistor
R2168K 1/4W Resistor
R3110K 1/4W Resistor
R411K 1/4W Resistor
R511K Linear Taper Pot
C111uF 16V Electrolytic Capacitor
Q112N3904 NPN Transistor2N2222, Most Small Signal Transistors
U11555 Timer IC
MISC1Board, Wire, Knob For R1, 8 Pin Socket For U1


  1. R1 adjusts the position of the servo.
  2. Connect the servo to the circuit as shown in the schematic. For common Futaba servos, the red wire is power, the black wire is ground, and the white wire is control.

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Simple Servo Controller
Wednesday, May 30, 2012 2:57:58 AM
what should we give in the controller?? i mean how should be the input?? could you give a table of inputs and the angle turned???
Simple Servo Controller
Thursday, November 03, 2011 3:55:25 AM
yesterday i assemble this ckt .this ckt does not work when i inserted the R2 resistor of 68 kilo ohm wit base of transistor in series
Edwin Smith
Simple Servo Controller
Tuesday, October 11, 2011 5:09:53 AM
I need some help changing this circuit. I have a single on of switch and want to us it to set the servo to minimum and maximum by simply turning it on or off. Will proley be good to have a variable pot in order to set the minimum/maximum position to fine tune. Please advise. I wanna make a number plate flipper for my bike with a servo. So On must be flipped up and off must be flipped down.
Simple Servo Controller
Sunday, July 03, 2011 9:38:42 AM
Question : can the other comparator be used to sense voltage drop in the vcc,and set different values for pin 6,as to make it switch H and V skew depending on receiver polarity?
Simple Servo Controller
Sunday, July 03, 2011 9:19:01 AM
I would like to suggest to add an IC where the pot is,and use the 13v/18v as reference to vary the resistance between 2 states for U1,in this way,you can feed the power from the LNB cable,and it will be possible to change skew according to polarity automatically.,with no power supply needed.
Simple Servo Controller
Wednesday, March 02, 2011 10:11:06 AM
Normaly, it will work with all kind of servo, maybe not with the digital ones..?!! But, like said in the comment uper, it is just a question of wire's color !
Simple Servo Controller:::::question
Wednesday, December 29, 2010 7:36:24 PM
is it working in other servo motor or only in Futaba servos?
Simple Servo Controller
Saturday, November 06, 2010 8:39:55 PM
Schematic not to clear U1 (555) Is Capacitor C1 postive side connected Pin (1) and to Pin (2) and Pin (6) of U1 (555) chip? mrel
Simple Servo Controller
Saturday, September 25, 2010 11:02:10 PM
Just like craig and john said earlier...I have the same problem too.All I need is to control the motor from 90 to 0 and 0 to 90.But my servo twitches once whenever I switch the circuit on.Please help me
Simple Servo Controller
Friday, August 06, 2010 2:14:50 PM
I hooked up the circuit on a proto board--it works pretty well, but I found it sort of noisy. In "Practical Electronics for Inventors," by Paul Scherz, it shows a 1000uF cap across the positive and negative inputs to the motor (page 933 of 2nd Edition). I tried a 5uF one and it cured the noise.
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