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Simple Servo Tester

www.GadgetGangster.com

The Simple Servo Tester is a must have tool for anyone into RCmodeling.

It will control up to two digital or analog servos without using atransmitter or receiver. All you need is a battery pack.

Use it to check your servos before installing them into your models.

Use it to center your servos when setting up linkages.

It can operate a servo throughout a wider range than most RCsystems. Approximately 0.800 milliseconds to 2.200 millisecondspulse widths. It can be tuned to precisely center your servos. Somemanufactures consider 1.520 milliseconds to be “center” others,

1.500 milliseconds.

Use it anytime you want to operate a servo but don’t want to getout your RC equipment.

http://www.gadgetgangster.com/





Assembly Instructions

Before you begin:

1. Knob2. Green LED3. NPN Transistor 4. Right angle pin header (9 pins)5. 555 Timer Chip6. Potentiometer

7. Trim pot8. Capacitors (2) 0.1 µF

9. Rectifier 10. Custom PCB11. 220k ohm resistor Red-Red-Yellow

12. 10k ohm resistor (3) Brown-Black-Orange

1

1 3 4

5

2

8

6

1011

9

7

12

Make sure you have all the parts






Step 1:

Press the knob onto the Potentiometer

Step 2:

Insert the 555 timer chip

Be sure that the notchfaces to the right aspictured here.





Step 3:

Insert Capacitors and Resistors


Insert the capacitors at C1 and C2, they are not polarized so itdoesn’t matter which way they go in.

Insert the four resistors. The 220k ohm (red-red-yellow) goes on theright. The other three 10K ohm go in the other spots. These also arenot polarized - but I like to put them in with the gold bands at thebottom. It makes no difference at all - just personal preference.

Bend the leads by holding ontothe component with one handand fold the leads together withyour fingers.





Step 4:

Start soldering!

! I like to use blue tape to hold the components in place.

Snip the leads after soldering.






Step 5:

Install the right angle pin headers

!

!

! Solder just the center pin of each header. Then pick up the board andreheat the center pin while applying pressure from the other side to snapit in place. This is an easy way to insure that the headers are flush andstraight.

!


Don’t forget to solder therest of the pins when youare satisfiedwith the alignment.

Snip apart the pin headersso that you have three of them with three pins each.





Step 6:

Install the NPN transistor, trim pot and diodes


Insert the rectifier diode as shown with the bandfacing to the right.

Place the green LED so that the shorter leg goesin the lower, square hole.

Bend the center leg a little bittoward the flat side of thetransistor.

Insert the transistor in theboard so that the flat sidefaces the 555 chip.





Step 7:

Solder in the Potentiometer

Place the potentiometer in position and solder just one pin at first - same aswith the pin headers - so that you can adjust it to be straight and flush with the

board before soldering it in for good.


Insert the trim pot asshown then solder them all in place.





Operation:

Hook up power

Always check for a green light before plugging in a servo.

!


The Simple Servo Tester has reverse polarityprotection for itself but it will not protect an attachedservo if you manage to hook up the power backwards.The green light will indicate that the polarity is correct.





Operation:

Hook up your servos


Plug in your servos, the polarity ismarked on the board.

The Signal line is usually White, Yellowor Orange depending on which brand of servo you are using.

Test for proper operation. If there is

erratic movement, or no movement atall it is most likely because of a badsolder joint or bridge. Unplug thebattery and servos and inspect all

joints. Re-solder any connections thatlooks suspicious.





Calibrate:

Adjust the center setting


Center the knob bylining it up with theline printed on theback of the board

Using a small screwdriver, adjust the trim pot untilyour servo is centered.

I have found that 1/8 to 1/4 turn clockwise is neededto center the servo.

All Done! Enjoy your new tool!



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