how can i easily convert 12v to 9v?
i want to hard wire my garage door opener into my car system.
thank you for suggestions.
Fish
how can i easily convert 12v to 9v?
i want to hard wire my garage door opener into my car system.
thank you for suggestions.
Fish
i found this post on the topic. if i remember right, i bought one of these zeners, and it has 3 leads coming out of it. how should i wire it into my car 12v dc circuitry? i want to put it inline if practical.
thanks again, fish
Hello fish,
Use a pre made design from Radio Shack so you don't do damage to your appliance. $18.95
Protection from surges and spikes with fuse protection is important.
Good Luck,
Temecula CA.USA
-- I think it would be _extremely_ inconveient, if not illegal, to drive around with that much wire coming out of your car.
that would work. the thrill for me is learning what makes something work, and implementing it in my environment. just buying the product from radio shack certainly isnt the fun route, for me, but it would get the job done. and then i wouldnt know how to reduce 12v to 9v dc if i wanted. thanks.
Usenet is not the place to start learning. The only "fun" you'll get by trying is to look like a troll.
First and most importantly; the "12V" electrical system is an 8 to
60V electrical system. Nominal operating voltage is around 14V.Based on your original requirements, you'd need a buck-boost regulator with heavily protected inputs. That's before you look at what the device actually needs.
Which is the second stage: Determine the actual power requirements of the device that you want to operate. "9V" because it nominally has a "9V" battery is insufficient information and probably misleading. You must at least measure the current draw and voltage when it's operating.
A better approach is to crack open the case on the device and do some reverse engineering on the power input stage. That should teach you a lot.
Third, you must look at what the door opener might be putting back onto the car's electrical system. It's quite likely that some radio-frequency signal component may be getting *backwards* through the regulator and could in theory even prevent the regulator from working or even have the regulator amplify (part of) the signal.
If the regulator continues to operate under those circumstances, then the whole car becomes a radio *transmitter* and will require FCC approval. :-)
Far better to filter out what could be "nasty" before it has the potential to be amplified by the voltage regulator.
There are an infinite number of solutions to a problem. A handful will be practical. Fewer will fit into your acceptability envelope when looking at cost, simplicity and perhaps reliability.
It's far more valuable for you to do some research on voltage regulation and automotive electrics than for somebody else to be blamed for supplying a detailed circuit which resulted in your door opener in exploding during a load dump or in the door opening or closing every time you crank the engine in the neighbourhood.
I've used several terms that you may not immediately understand. Google for them for elucidation.
-- /"\ Bernd Felsche - Innovative Reckoning, Perth, Western Australia \ / ASCII ribbon campaign | "Laws do not persuade just because
no problem!, i work at a wire factory!, how miles did he said he needed to travel ?
-- Real Programmers Do things like this. http://webpages.charter.net/jamie_5
Will the IC 7809 Regulator do the job?
fish wrote:
Will the IC 7809 Regulator do the job?
fish wrote:
google "voltage divider" and you will see an easy way to do it with resisters.
The car voltage varies, it isn't necessarily 12 volts - that is only the nominal voltage. A zener isn't the best choice for this.
Use an LM7809 three terminal regulator and switch it on and off with the accessories or ignition circuits. The regulator will give you a stable 9 volts out. You "should" provide transient protection - but they are pretty rugged even if they don't have transient protection.
Cost ~50 cents in the 1 amp TO220 package (more at Radio Shack)
They can't be connected backwards - that kills them quickly. Read up on 3 terminal regulators - there are several caveats to observe if you want to do it right - but just wiring input, output and ground will probably work and last forever (or until someone connects some booster cable backwards).
data sheet for LM340/LM78XX parts - 09 is the 9 volt regulator Look at the application hints and notes if you want to understand how to use it.
Search for National Semiconductor site for more information. They are good about giving out databooks and have their entire website on CD for easy searching and it was free the last time I checked.
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thanks very much.
Fish
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And allow for the possibility of the door opening/closing when cranking the engine of the car because the supply voltage could fall pretty close to 8V.
Depending on the door opener, it may see the hiccup as a command to open/close the door. Most people will not want that to happen at that point in time.
-- /"\ Bernd Felsche - Innovative Reckoning, Perth, Western Australia \ / ASCII ribbon campaign | "Laws do not persuade just because
yes., just make sure you attach it to a heat sink and not go over 1 amp of current.
-- Real Programmers Do things like this. http://webpages.charter.net/jamie_5
Garage door opener? sucking down significant current? Unlikely.
Tops would be about 100 milliamps, and it might be more like 10 ma -
FCC rules probably limit the transmitter to 100 milliwatts and that's
11 milliamps and reasonable for a 9 volt battery. Chances are the TO92 regulator would work since it is capable of ~100 ma without a heatsink.I bought a tube of surplus T220 9 volt regs some time ago and use them in projects. Most of the time I just cut the heatsink tab off to save space. No problem pulling 250 ma with a 12 volt input and no tab or heatsink with 12 volt in.
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Quite frankly, it would be rather clumsy (in my opinion) to have your garage door remote powered permanently from your car cig lighter outlet. The cable would get caught up whenever you tried to move something and could cause more problems than it is worth. Remotes draw so little current that a standard 9V alkaline battery lasts for years. I have had my automatic garage door installed for about 9 years now and I have only changed the remote battery once.
Perhaps you're making this more of a problem than it need be. Here's how I did it: Installed a push-button switch in the dashboard wired across the remote transmitter's switch. Installed the remote transmitter high up under the (plastic) dash in a wad of foam rubber. I replace the 9 v battery (a lithium type) religiously every 5 or 6 years. Works like a charm and there are no interface issues.
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