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Step Down Voltage Regulator Question

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This is my first post so please excuse me if selected the wrong category to post in. Electronics is not my field of expertise so if I come across as being ignorant then I'm guilty.

I'm using a Digilent 210-156 step down voltage regulator to power a LiftMaster remote garage door opener. My plan was to use an existing switch such as the horn to provide intermittent 12VDC Input but that doesn't work.

Switch Input current off and the Output is 0VDC.
Switch Input current on and the Output is 3.33VDC.

That should make the remote opener transmit a signal but it doesn't. With constant 12VDC Input switching the Output positive makes the remote opener transmit a signal

If I leave the Input hot and then switch the positive Output then it works. Is there an explanation for that behavior?

Ron Becker

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  • 3 weeks later...


I apologize for the delay.

I want to make sure I understand your setup and what you are experiencing correctly; if you only intermittently provide power to the VRM by turning on your switch (in your example, the car horn), which correspondingly provides power to the garage door opener, no signal is transmitted? I have attached a generic sketch of how I am imagining this setup to look.

Presuming the above is the case there are a couple of things that can think of that might be contributing to the problem (and other things)

- The garage door opener needs more time to "power up" before it can send a signal. This would explain why leaving power attached and then enabling the regulator (disable the regulator by pulling the Enable pin to ground and unattach it/leave it floating to enable the regulator) does successfully cause the remote to work.
- The garage door opener expects a slightly different voltage. I'm guessing that the remote uses two AA batteries which usually works out to around 3V. Providing 3.3V might work, though depending on the internal circuitry of the garage door opener it might have it's electronics wear out sooner than you expect.



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