Electrical Question

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Model T Ford Forum: Forum 2018: Electrical Question
Top of pagePrevious messageNext messageBottom of page Link to this message  By Glenn W. Beers / Kunkletown, Pa on Monday, January 22, 2018 - 02:10 pm:

I would like to use the ignition switch to power a relay. The question is do any of the terminals stay hot when you turn the switch on in any position and off when done ?

Thanks
Glenn


Top of pagePrevious messageNext messageBottom of page Link to this message  By George n LakeOzark,Missourah on Monday, January 22, 2018 - 02:19 pm:

Yes, the solid yellow wire on terminal block . Usually #3 position . Yellow wire comes from battery from batt. side of starter switch.
I use it for my Garmin and phone.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Bruce Compton on Monday, January 22, 2018 - 03:17 pm:

So.. can I use this terminal for my direction lights? I've killed the battery a few times now when I parked the car with the direction lights still on. I thought with this wiring, I would lose power to the direction lights if I switched to "mag".


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jerry VanOoteghem S.E. Michigan on Monday, January 22, 2018 - 03:46 pm:

The yellow wire is always "hot", no matter where the switch is positioned.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Bruce Compton on Monday, January 22, 2018 - 04:24 pm:

Glenn's question was to use the ignition switch to power a relay, so I assumed he wanted to be able to turn the power on and off with the ignition switch. I want to do the same thing and be able to de-power my direction lights with the ignition switch and not lose power to the direction lights when I switch to "mag"


Top of pagePrevious messageNext messageBottom of page Link to this message  By Glenn W. Beers / Kunkletown, Pa on Monday, January 22, 2018 - 06:24 pm:

Bruce, you are correct I want to turn the relay on and off with the switch to power a pump.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Bruce Compton on Monday, January 22, 2018 - 06:39 pm:

I'm a little "electrically handicapped" but can't see a way to have switched 6VDC power as it would not be there when the switch is in the "mag" position


Top of pagePrevious messageNext messageBottom of page Link to this message  By Glenn W. Beers / Kunkletown, Pa on Monday, January 22, 2018 - 06:48 pm:

That is what I assumed but I thought someone might know differently.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jim Davis on Monday, January 22, 2018 - 08:03 pm:

I can see Several ways to do it, use a electrical latching relay which can be a normal relay with multiple contacts that when it is energized applies voltage to itself to keep relay closed, without the need for power from either the Battery or mag position on the Ing Switch would need a small push button sw to break the connection and turn off the relay powering the turn signals or pump when car is parked, another way would be to use a second relay which is normally off with voltage to the main relay going through it and when You hit the horn it would reset or turn off the first relay and to reactivate it just turn ing switch to battery for a split second, easiest way I see is a a/c relay that would handle mag voltage or DC relay with a diode connected to the coil position and when you switch to Mag it would activate might activate on Battery too depending on relay used ? I have not tried any of these methods but based on my 60 years of electronic work You should be able to fine a way that will work best for You.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mark Gregush Portland Oregon on Monday, January 22, 2018 - 08:04 pm:

Add it's own switch. As said you can have power all the time or only when the key is turned to battery.


Top of pagePrevious messageNext messageBottom of page Link to this message  By John F. Regan on Monday, January 22, 2018 - 10:28 pm:

You can do it on a typical black T car by adding a diode and a light bulb to your relay circuit BUT you MUST choose your relay rather carefully. A typical DC relay takes less current to "hold" it in the operate state than it does to first turn it on and get it to operate. You can take advantage of that. Thus you can put a diode and small bulb in series with the relay winding and connect the anode of that diode to the coil box connection and when you have the coil box running on 6V DC the bulb should be dim and thus have a low resistance and when you switch to mag the bulb should light up brighter and rectify the AC on the coil box but if chosen correctly the bulb will prevent the relay from loading the magneto voltage very much at all and the relay should stay operated so long as the engine stays running and until you shut off the magneto.

The trick is to select the correct relay very carefully. This scheme would work with anything you want to power directly from the battery whenever the key is in either the BAT or MAG position. There are other electronic devices like optic isolation devices that might do the job of relay driver but a 1N4007 diode (cost about a nickle) and a small bulb - as yet unknown and the small relay is all you need. You start by figuring or measuring the amount of DC current you need from the battery for the lights or pump or whatever it is. Then you find a relay that is very sensitive and needs very little operate current but can switch the load current you measured. Then you pick the bulb. If you can't find such a relay you can then pick a heavier current one and add one transistor to your circuit to have the bulb and diode turn on the transistor which in turn "drives" the relay. All of this is pennies except for the relay. Most the electronic gurus on this forum understand what I am proposing and can draw you up a schematic or if you draw one up and send it to me I will correct it if you have something wrong. But FIRST find out how much current you are going to try to pull from the battery when the relay is operating.

Have fun.

John


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jim Davis on Monday, January 22, 2018 - 10:44 pm:

Another solution would be to just add a master switch that turns the power off to every thing except the main Battery to starter switch Buss wire, it could be one of the big turn key master switches or it could be a relay that turns power off which is activated by a small switch which could be hidden under the front seat or dash and serve both a master power switch and a kill switch, to protect the car from unauthorized operation, with the added benefit of disconnecting the entire electrical system when the car was parked or Garaged.


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