A small 12v to 9v project; help needed

In summary, the conversation is about a project where the person wants to hardwire a 9v garage door remote into their motorcycle's low-beam circuit. They are looking for a way to drop the voltage from 12v to 9v to power the remote for short bursts of time. Options such as using a single resistor, zener diodes, and voltage regulators are discussed. The person ultimately decides to use a LM7809 voltage regulator and thanks everyone for their input.
  • #1
ManiZ
4
0
Hi guys. I have researched this topic A LOT. In fact, I found these forums as a result. Evidently, it has been asked here before (Google knows all!). Mine has a slight twist to it. All the research I have done so far has been about people wanting to run a continuous 9v load off a 12v source. Mine will be for a fraction of a second at a time.

Project: I want to hardwire a 9v garage door remote into my motorcycle's low-beam circuit. The jumpers under the activation button on the remote will be soldered together so as to keep it permanently primed to send the pulse if power is provided. I would then solder wires into the remote's battery terminals and splice the positive wire into the power wire of the low-beam circuit while -ve will naturally be grounded. I always ride the bike with my high beam on so the idea is to get close to the garage, switch from high to low for a fraction of a second and switch back. That should open/close the door.

Questions:

- Do I even need to drop the voltage if I will be powering the remote for such short bursts? If for any reason, I am forced to have the low-beam on for an extended period (i.e. the high-beam coil burns out while on an unlit road at night), would it immediately fry the remote's circuitry?
- I was thinking of using a single 1K Ohm resistor and wiring it in series with the low-beam wire and the remote. I came across http://www.bcae1.com/resistrs.htm which suggests that per Ohm's Law a resistor in a circuit takes all the load, BUT they don't say what would happen in my proposed scenario if the voltage is measure forwards of a single resistor. I am sure it would drop somewhat.
- My research has pointed me to zener diodes as well. But I am thoroughly perplexed by how they work. Are they the answer?
 
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  • #2
LM7809
UTC-LM7805-pinout.jpg

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LM7812-pinout.jpg


http://mipsa.p.lodz.pl/download/BazaWiedzy/zasilania/LM7805.pdf" [Broken]
 
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  • #3
That was fast! Thanks. I will look into it. Seems to be hard to find online but I will call a few places to check.
 
  • #4
Why not just put a 3.3V Zener in series with the 12V line going to your remote?
 
  • #5
Zener option was one of my 3 questions in the original post. But it does appear that it only drops the voltage and cannot regulate it. The bike does not put out a constant 12v, it can vary from 12-14v depending on the load on the battery. So the voltage regulator option seems best because even if I do have the low beam on for an extended period, it will not harm the remote.

I used one of the stickies in this forum to find LM7809 for sale on several websites, one of which was of my own employer (Arrow Electronics)!. I am in a completely different division and had no idea we even sold such components. So I now have 3 x LM7809 on their way and hope to complete the project by Monday. Thanks to everyone who viewed this thread!
 
  • #6
ManiZ said:
...
But it does appear that it only drops the voltage and cannot regulate it
...
Not!

260px-Zener_diode_voltage_regulator.svg.png
 
  • #7
Using a 9 volt Zener in conjunction with a load resistor will provide a constant 9 volts as long as the supply is greater than 9 volts. Using the diagram above.
 
  • #8
I don't know which brand of garage door opener you have but generally they are not very sensitive to battery voltage. The receivers are super-regenerative with a receive bandwidth of about 1.5 MHz. A little frequency shift won't hurt you and I think the main effect of varying voltage would be a variation in range. I suspect that the components would survive operation on 12 V instead of nine.

Thus my suggestion to use a 3.3 V zener or perhaps just a dropping resistor would be sufficient. By the way most Chamberlain garage door openers do work on 12 volts though if you don't have Chamberlain system that won't help.
 
  • #9
skeptic2, I wish you had posted that sooner! I had read that many 9v devices can run on 12v but wasn't sure if garage door remotes do as well.

It is a Wayne-Dalton system. They used to make a 12v remote for my model but recently discontinued it and even calling their corporate office directly didn't bring about any success. It was the first thing I tried.

Chamberlain makes a popular universal remote that would work with my system (303MHz) but it operates on 6v so an even larger drop to contend with. Genie is one brand that almost exclusively has 12v-only transmitters but they don't make a universal model.

Since I have the LM7809 on the way already, I will go with that option. It seems to be the simplest of them all as well since (based on Xitami's diagram) wiring it alone in series is all that's needed. Thanks for everyone's continued input!
 

1. How do I convert 12v to 9v?

To convert 12v to 9v, you will need a voltage regulator. This device will regulate the voltage and provide a steady 9v output. You can purchase a 12v to 9v voltage regulator or build one yourself using basic electronic components.

2. What components do I need for this project?

To complete this project, you will need a 12v power source, a voltage regulator, a 9v battery, and some basic electronic tools such as a breadboard, wires, and a soldering iron. You may also need additional components depending on the specific design of your circuit.

3. Can I use any 12v power source?

It is important to make sure that the 12v power source you are using can handle the load of your project. Some power sources may not be able to provide enough current for your circuit, which can cause damage. It is recommended to use a power source with a higher current rating than what your circuit requires.

4. How do I test my circuit?

Before connecting your circuit to the 9v battery, it is important to test it with a multimeter. You can use the multimeter to measure the output voltage and make sure it is at a steady 9v. You can also test the circuit's current draw to ensure it is not exceeding the capabilities of your power source.

5. What if my circuit is not working?

If your circuit is not working, there could be several reasons. Double-check all connections and make sure they are secure. Check the voltage regulator to make sure it is functioning correctly. If necessary, try using a different power source or replacing any faulty components. Troubleshooting electronic circuits can be complex, so it may be helpful to consult a professional or seek guidance from online resources.

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