Use it to check your servos before installing them into your models or to center your servos when setting up linkages. The Simple Servo Tester can also be tuned to precisely center your servos - Some manufactures consider 1.520 milliseconds to be center while others use 1.500 milliseconds.
Use it anytime you want to operate a servo but don't want to get out your RC equipment!
This project was designed by W9GFO. You can get the kit from Gadget Gangster and download a PDF version of this howto.
Warm up your soldering iron and get started!
Step 1: Make: Parts List
- Potentiometer Knob
- Green LED
- NPN Transistor
- Right angle pin header (9 pins)
- 555 Timer Chip
- 20k Right Angle Potentiometer
- Trim pot
- 2x Capacitors (0.1 uF)
- Custom PCB
- 220k ohm resistor (Red-Red-Yellow)
- 3x 10k ohm resistor (Brown-Black-Orange)
Step 2: Make: Potentiometer Knob
Step 3: Make: 555 Timer
Step 4: Make: Prepping the Caps & Resistors
Step 5: Make: Adding the Caps & Resistors
The 220k ohm (red-red-yellow) goes on the right. The other three 10K ohm go in the other spots. These also are not polarized - but I like to put them in with the gold bands at the bottom. It makes no difference at all - just personal preference.
Step 6: Make: Start Soldering
After soldering, snip the leads.
Step 7: Make: Install the Right Angle Pin Headers
Solder just the center pin of each header. Then pick up the board and reheat the center pin while applying pressure from the other side to snap it in place. This is an easy way to insure that the headers are flush and straight.
Don't forget to solder the rest of the pins when you are satisfied with the alignment.
Step 8: Make: Install the NPN Transistor and Diodes
Insert the rectifier diode as shown with the band facing to the right.
Place the green LED so that the shorter leg goes in the lower, square hole.
Step 9: Make: Install the Trim Potentiometer
Step 10: Make: Solder in the Potentiometer
Step 11: Operation: Hook Up Power
The Simple Servo Tester has reverse polarity protection for itself but it will not protect an attached servo if you manage to hook up the power backwards. The green light will indicate that the polarity is correct.
Step 12: Operation: Hook Up Your Servos
Test for proper operation. If there is erratic movement, or no movement at all it is most likely because of a bad solder joint or bridge. Unplug the battery and servos and inspect all joints. Re-solder any connections that looks suspicious.
Step 13: Operation: Adjust the Center Setting
Using a small screwdriver, adjust the trim pot until your servo is centered. I have found that 1/8 to 1/4 turn clockwise is needed to center the servo.
ALL DONE! ENJOY YOUR NEW TOOL!