I'm working on a 555 timer oscillator circuit, and I'm trying to get an LED to blink. The LED turns on, but I'm not sure if it's blinking. I do not own an oscilloscope I've tried a few things, such as recording with a slow motion camera. Is there a good way to test it? I was thinking I might be able to hook up a transformer to it and check for a constant voltage.
Use a RC low-pass filter and a multimeter.
- Connect a 10 kΩ resistor to the point you believe is oscillating.
- Connect a 10 µF capacitor between the resistor and ground
- Measure the voltage across the capacitor, let's call this voltage \$V_c\$
If \$V_c\$ is around 20-80% of the max value of the signal you believe is oscillating, then it's most likely oscillating.
If \$V_c\$ is around +99% of the max value of the signal you believe is oscillating, then it is most likely not oscillating.
Using a low pass filter in this configuration will give you the average value of the oscillating signal. So if it is 50% high and 50% low and it is a square wave signal that is between 0 V and 5 V. Then in an ideal world you will read 2.5 V across the capacitor.
If it is high 80% of the time then you will in an ideal world read \$0.8×5=4\$ V across the capacitor.
If it is high 100% of the time, then it's not oscillating, and you will therefor read 5 V.
You could try to take a movie of your LED at a high rate. I think most smartphones can film at 60 Hz. Plot the amplitude of the pixel associated with the LED and see if there is a distinct frequency. You might be able to say if your LED is blinking but might not be sure about the frequency due to aliasing.