- #1
roeb
- 107
- 1
Hey, I'm trying to build a stroboscope for measuring the RPM of a few different fans.
So far I've tried using LEDs but haven't been very successful. I tried using a function generator with square pulses (I tried both 20% duty cycle and 50%). So I started at 1 Hz and kept on increasing the frequency. Unfortunately, the small square of tape that I put on the face of the spinning fan (as well as the sticker) never really came into focus. I could see it kind of slow down, but then it never quite got to the point where it was strobing at the same frequency (I adjusted down to a tenth of a Hz).
The fan I'm using as a test subject does indeed have a tachometer so I know I was running it at about 4000 RPM. If I'm not mistaken I should have been able to get the strobe in synch at about 67 Hz. Unfortunately, I could never really get it to work.
The circuit itself is just a few LEDs in series with a 100 ohm resistor, I adjusted the voltage to make them fairly bright. I put this on a breadboard, but I'm assuming that the capacitance of the breadboard shouldn't have an effect at such a low freq (0 to 100 Hz).
Does anyone have any hints on how to accomplish this? As far as I know LEDs would work for this purpose. I feel like it would be better if the duty cycle were lower, but my function generator only goes down to 20%.
Thanks
-roeb
So far I've tried using LEDs but haven't been very successful. I tried using a function generator with square pulses (I tried both 20% duty cycle and 50%). So I started at 1 Hz and kept on increasing the frequency. Unfortunately, the small square of tape that I put on the face of the spinning fan (as well as the sticker) never really came into focus. I could see it kind of slow down, but then it never quite got to the point where it was strobing at the same frequency (I adjusted down to a tenth of a Hz).
The fan I'm using as a test subject does indeed have a tachometer so I know I was running it at about 4000 RPM. If I'm not mistaken I should have been able to get the strobe in synch at about 67 Hz. Unfortunately, I could never really get it to work.
The circuit itself is just a few LEDs in series with a 100 ohm resistor, I adjusted the voltage to make them fairly bright. I put this on a breadboard, but I'm assuming that the capacitance of the breadboard shouldn't have an effect at such a low freq (0 to 100 Hz).
Does anyone have any hints on how to accomplish this? As far as I know LEDs would work for this purpose. I feel like it would be better if the duty cycle were lower, but my function generator only goes down to 20%.
Thanks
-roeb