increasing voltage from 4 > 12?

Printed From: the12volt.com
Forum Name: Relays
Forum Discription: Relay Diagrams, SPDT Relays, SPST Relays, DPDT Relays, Latching Relays, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=12465
Printed Date: May 15, 2024 at 6:23 AM

Topic: increasing voltage from 4 > 12?

Posted By: brivalen
Subject: increasing voltage from 4 > 12?
Date Posted: April 20, 2003 at 1:27 PM

I am trying to install a new power antenna in a 2000 Lexus RX300 - the remote turn on lead in only giving me 4~5 volts and I need 12 for the new antenna. How can I accomplish this? The 4volts was not enough to turn on a relay (wired as a remote turn on thing like on the relay example page on this site).

Any help would be appreciated

Brian

Replies:

Posted By: vaderfop
Date Posted: April 20, 2003 at 9:46 PM

you could wire it off of the +12 volt switched wire for the radio, the only problem with this si that the antenna will go up when ever the car is on, not just when the radio is on.

Posted By: TomEllis
Date Posted: April 21, 2003 at 10:29 AM

You could also get a 5 volt relay instead of the 12 volt one you tried.
You can find them at "Digi-Key" or "Mouser".
do a search for relays.
Good luck,
Tom

Posted By: Thinkster
Date Posted: April 28, 2003 at 8:46 PM

Why do they gotta do things non-standard? Oh I know why, they want you to buy an original Lexus Power Antenna so they can charge you like $200+. Anyways, I would say you might be able to use a DC-DC converter if it doesn't require a lot of current for the trigger. Otherwise as the other poster stated, you can get lower voltage relays that should work at 5V. Of course they are not in the same configuration as a standard P&B or Bosch Relay, but as long as the coil and contacts are all identified, you should be able to figure it out.

Posted By: 89burban
Date Posted: May 02, 2003 at 11:45 AM

If your into electronics, you could use a npn transistor with the right resistor combination to give you the 12 volts you need

Posted By: demeanor
Date Posted: July 02, 2003 at 9:37 PM

hey 89 burban...can you be a little more specific???
TIA

-------------
It's better to ask a "STUPID" question...than to know a "STUPID" answer. :-)

Posted By: 89burban
Date Posted: July 03, 2003 at 5:58 AM

https://www.williamson-labs.com/480_xtor.htm

That was the only site I found that explains clearly how a transistor works. In your case you have a low dc signal that you would like to be 12V, there are three leads on the transistor, base,collector, emmitter. There are a bunch of different configurations, but i think the one you might want to use would be the common emitter. The base lead of the transistor would be tied to the small dc voltage, the collector would be tied to the 12V and the emitter would be the common ground between the two. A transistor has a multiplying factor, called beta, meaning that the amount of current that is flowing through the base is multiplied by the beta, could be 100, 200 ,300, you have to check. I dont think you will have to worry about this 2 much, as you are using it as a switch, so it will be either off or on. Depending on the size of the small dc voltage you might have to experiment a bit to get the right resistor combination for your application. So what should happen is, you turn on whatever is supplying the small dc voltage, the current from this flows through the base of the transistor, causing much greater current to be drawn through whatever your load is, then to the collector from the 12v source, and all the current flows out through the emitter. I dont know how much current is needed, but even if you cant use this to power the antenna, it might be useful to power the trigger on the relay that THINKSTER was talkin about. I'm doin this from memory, so i'm probably gonna get burned fer not knowin what i'm talkin about, but there it is ;-)

Posted By: xetmes
Date Posted: July 03, 2003 at 6:38 AM

You could use an NPN transistor, If it is giving you 4 volts out: Put a 330 Ohm resistor on the base of the transistor, the other side to the 4 V source, tie the emitter to ground, the tie the collector to one leg of a 12V relay coil, hook the other leg of the coil to +12 V. You may want to put a diode on the input (before the resistor), and a resistor (like 1 K) to ground to clamp off some ringing, maybe a small cap too.

Posted By: jgold47
Date Posted: July 03, 2003 at 1:32 PM

jesus....I need to do something similar with a led output from my alarm....I get a 2v output, but want to use 12v led's...I dont know if the 2v will throw the relay or not...obviously if it does I am fine, but if not....what would people suggest?

Posted By: xetmes
Date Posted: July 03, 2003 at 4:07 PM

I dont think you would run a relay from the flashing (im assuming) LED, it would be clicking on and off and drawing much more current thank the led, Just use the transistor in the same manner but with a 130 ohm resistor