servo tester using 4538


Posted on Feb 6, 2014

There are times when a small servo tester for modeling comes in very useful. Everybody who regularly works with servos will know several instances when such a servo tester will come in handy. The function of a servo tester is to generate a pulsing signal where the width of the positive pulse can be varied between 1 and 2 ms. This pulse-width deter


servo tester using 4538
Click here to download the full size of the above Circuit.

mines the position the servo should move to. The signal has to repeat itself continuously, with a frequency of about 40 to 60 Hz. These circuits often use an NE555 or one of its derivatives to generate the pulses. This time we have used a 4538 for variety. This IC contains two astable multi-vibrators. You can see from the circuit diagram that not many other components are required besides the 4538. The astable multi-vibrator in a 4538 can be started in two ways. When input I 0 (pin 5 or 11) is high, a rising edge on input I 1 (pin 4 or 12) is the start signal to generate a pulse. The pulse-width at the output of IC1a is equal to (R1+P1)G—C1. This means that when potentiometer P1 is turned to its minimum resistance, the pulse-width will be 10 k G— 100 n = 1 ms. When P1 is set to maximum (10 k), the pulse-width becomes 20 k G— 100 n = 2 ms. At the end of this pulse inverting output Q generates a rising edge. This edge triggers IC1. B, which then generates a pulse. The pulse-width here is 82 k G— 220 n 18 ms. At the end of this pulse the Q output will also generate a rising edge. This in turn makes IC1. A generate a pulse again. This completes the circle. Depending on P1, the total period is between 19 and 20 ms. This corresponds to a frequency of about 50 to 53 Hz and is therefore well within the permitted frequency range.




Leave Comment

characters left:

New Circuits

.

 


Popular Circuits

10 Watt Audio Amplifier
Audio Mixer with 2N3819
Breadboard header for ATTiny
One transistor LED Flasher
Waveform generator II
Low loss brightness control
Musical chime generator
Low-forward-drop-rectifier-circuit
250W Inverter Circuit
Automatic blind hooked up to existing projector screen using Arduino
F/V Converter for Tachometer Bar Graph Display
audio-video modulator circuit
im3500
Automatic headlight dim switch
Telegraph Transmitter in the Pilot Radios Radio Design magazine 1930s
Preamplifier For Soundcard
ESL amplifier circuit diagram
Automatic telephone call recording circuit



Top