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Step motor kontrol devresi – Stepper Motor Controller
R1 = 18K
R2 = 680K
P1 = 50K Potentiometer (Linear)
C1 = 0.033uF
C2 = 0.1uF
IC1 = LM555 Timer (or equiv.)
D1 = 1N4148 Additional Notes: The circuit above speaks for itself and does not need any more explanation, in my opinion. The Servo control arm can sweep from 1 to 2mSec at approximately 7mA (4.8 volt assumed). PPA is 4 volt at a frame rate of 16 mSec. This is a cheap and worthwhile project. Not only can you check the proper working of your servos you can also check for 'drag' or excessive rubbing when the servos are installed in your aircraft. Radio Shack part numbers are available.
Servo Tester Using A 4538
There are times when a small servo tester for modelling 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 determines 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.
Circuit diagram:
The pulse-width at the output of IC1a is equal to (R1+P1)×C1. This means that when potentiometer P1 is turned to its minimum resistance, the pulse-width will be 10 k × 100 n = 1 ms. When P1 is set to maximum (10 k), the pulse-width becomes 20 k × 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 × 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.
