HiLetgo 5pcs NE555 Pulse Frequency Square Wave Rectangular Wave Signal Generator Signal Generator Module Stepper Motor Driver DC 5V-15V Powered

I bought because of the price! These 555-based, signal generator circuits are well built and I was able to set the desired frequency following the comments written by another reviewer.

I don’t mind building 555 timers but why when these are already to go.

Very handy if garage door eye beams are a problem. Can be used to fool your door opener by substituting for the traditional ankle-high eye beams. In my situation, the beams would frequently get in the way. Although I suppose that they're useful for other applications requiring pulse generation, I took off a star because nothing is included suggesting how to actually implement their use on a door opener, nor that a diode--purchased separately--is also required.

All worked fine, great value

These work great! I used them to retrofit CAN Bus controlled seats from and E90 BMW into a vintage car. They act to trick the module so they don’t time out as otherwise you would have to cut power to adjust the seats after being powered up for 10 or so seconds.

Bypass garage door sensors and it works so well. Use extreme caution when bypassing any safety device. Not recommending if you have pets or children. Many other uses for the 4 units remaining.

There's no documentation provided, but it's easy to find the circuit online or simply to trace it out. Obviously the two adjustment pots are not independent, and achieving any specific timing takes a decent oscilliscope and patience, but for rough work you don't need this. I glued two metal pins (power & ground) into the holes provided for mounting, wire wrapped them to the already existing power pins, and these guys now plug perfectly into a standard breadboard.

They all turned on for a brief moment and then stopped working, tested with multiple power supplies and result was the same each time.Also they came with no instructions. Gotta love that top shelf CCP work ethic and craftsmanship