DST Digital Servo Tester / LCD Tachometer

DST V 3.24

Digital Servo Tester / Tachometer, Four in one -- 16F84A    

for DST V 4.X visit here


=====   Acknowledgements 2010/01 ==================

Fred <micowave@clix.pt>  from Azores islands, Portugal. offer PCB layout for both V3.X and V4.X.

Here is the V3.X . Download lay file DST_Fr84.zip


V3.24 update: FIX bug, when doing receiver testing may crash at 1500uS. thanks to "ysniwo" from Taiwan who reported the bug.@

V3.23 Update

Due to some strange LCD modules (C1602B-xxx) can't operate normally, but display two black line, with the V3.22. I do some modification to make the program fit all LCD modules I have had.


Andrey offer a new layout here with LM358 front-end

Thanks to Andrey again.   The .lay file  can open by  "Sprint Layout"  program


The Hardware V1.1C  DST.sch with LM358 front-end, others same as V1.1

For higher sensibility, the front end of Tachometer, use a LM358 IC instead of 2SC945.

This circuit can read  scintillation of scintillant light, easily.



Hardware V 1.1 with 2SC945 front-end


Digital servo tester (DST)      

Full digitize, 10 uS / step, 20mS / frame, have five test modes:

1. Manual mode

the PWM pulse width range from 1000uS~ 2000uS, 10uS/step with one touch neutral point (1500uS).

2 .Slow mode

take 10 second from 1000 to 2000 and reverse too, auto process 2 times 

3. Fast mode

Jump between 1000 and 2000 every 0.5 second, auto process 5 times 

4 .Mid mode    

take 2 second from 1000 to 2000 and reverse too, auto process 5 times 

5. Random mode          

Random Jump  every 0.3 second, auto process 20~30 times 


Receiver tester (REC_T )    

Function: read out receiver's output PWM width, and test the sticks of transmitter.

For this test, you need a connecter like this with two female end. 

You can connect two ordinary servo cable to get this.



Speed Controller Tester (SCT)

The PWM pulse width range from 1000uS~ 2000uS, 10uS/step with one touch stop (1000 uS)..

The initial pulse width is 1000 uS.


LCD Tachometer   

range from 100 RPM to 99900 RPM,   100 RPM resolution for 2 to 5  blades propeller

accuracy 100~ 10000  +- 100 RPM,    10000~99900 +- 1% , refresh rate 0.6 second / time


Operation Manual: here

DIY tips:    

Remember to connect CD4013 pin 3,4,5,6,7,8,10 to GND,  pin 14 to VCC, and a 0.1 uF between pin 7 & 14

For more detail & DIY , see the LED Tachometer for ref.

More picture about the prototype pic1  pic2  pic3


1. The 5 mm phototransistor is L-51P3C . any 3~5 mm phototransistor work with hardware V1.1C

2. Three lead phototransistor is OK. just let the "B" unleaded.

3.  LCD module is WH0802A from WINSTAR, almost any brand will do, even a 16*2. the pin count are all the same.


16F84A.ASM  V3.24                         16F84A.HEX   V3.24



You MAY duplicate, modify, give away or sell the original files in the web site or anything you derive from it.

ATTENTION : It is your own responsibility, if any damage cause by using the web site.

Philip Sun / TAIWAN


copyright 2004