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Charles, Marine Tech
Category: Marine Electronics
Satisfied Customers: 3707
Experience:  US Navy (Ret) I have been installing Marine Electronics for over a decade now.
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How can I setup a wiring system so that: a 12v switch

Customer Question

How can I setup a wiring system so that: a 12v switch controls a 24v switch. In other words the 24 volt switch in a 24 volt line turn on and off by a 12 volt switch on a 12 volt line.
I have a 24 volt engine ignition switch that I'm trying to incorporate into an alarm system that is on a 12 volt system. I could go with a 12v to 24 volt step up power transformer but I don't feel comfortable for the ignition to really get the 24 volt power that it needs. I want a setup or adaptor that can tell the 24 volt power source for ignition to turn on and off when the 12 volt switch is turned on and off.
Submitted: 6 months ago.
Category: Marine Electronics
Expert:  Jason replied 6 months ago.

Hello my name is Jason.

I don't really understand your question. What are you trying to do exactly? Do you have any kind of wiring diagram that I can look at so I can try to get a better idea of what you are trying to do?

Customer: replied 6 months ago.
Ok. I added a drawing. I'm looking for a way to use a 12v switch to tell the 24v line to turn on and off.
Expert:  Jason replied 6 months ago.

What is the power source going to be? Is this AC or DC? Are you using transformers or batteries?

Customer: replied 6 months ago.
It's DC I believe. Runs on batteries. The ignition is from 2 12v batteries configured to run on 24v. The 12 volt is from one battery for accessories. There has to be a module or switch that uses a 12 v power source to turn a 24v line on and off. I could use a step up transformer after the 12v switch to the ignition but prefer to have the 24 v ignition by the original 24 volt power source.
Expert:  Jason replied 6 months ago.

Are you using a 24V battery or 2 12V batteries in series to make 24V?

Customer: replied 6 months ago.
2 12v
Expert:  Jason replied 6 months ago.

Voltage travels in loops, so all you need to do is run power from 1 of the 12V batteries to your switch, and then from that switch to your load. Then ground that load back to that same 12V battery that you are using for the power wire. I'm adding a picture, let me know if this does or doesn't make sense to you.

Expert:  Jason replied 6 months ago.

Does that make sense to you?

Expert:  Jason replied 6 months ago.

If you had a further question on the issue by all means feel free to ask. If not, Just in case you do not understand the way the website works (and some folks do not). You do have to put forth a positive rating in order for it to credit me for helping you. When ratings are not done, the website simply keeps your deposit and they will not credit me. The ratings box is located at the top of the screen. To rate, you must select the star you wish and also confirm it. Please let me know if you run into any problems or errors when trying to do it. If you do have a problem, or if you can not see the ratings box which is at the top of the screen. Please reply back "I rate Jason's service _______" and fill in the blank.

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Thank you

Customer: replied 6 months ago.
My question is how can I use the 12 volt switch to turn the 24 line on and off.
Expert:  Charles replied 6 months ago.

Hello, my name is***** will assist you from here. I would need to know what type of switch are you going to use to control the alarm, and if the 24V is just for the starter or is it also for battery charging?

Customer: replied 6 months ago.
The 24 volt is just to engage ignition.
Expert:  Charles replied 6 months ago.

Thanks. What engine is this? I would like to look it up.

How are the batteries recharged after starting the engine?

Customer: replied 6 months ago.
It's for a HMMWV. My problem is just to turn the on/off 24V line with a switch that is powered by 12V. So line A is a 24V power supply and when engaged it turns the ignition on. Line B is 12V and it powers the 12V alarm system and has a 12V ignition switch. I would like to use the 12V alarm switch as the signal for on and off for 24V line A.
Expert:  Charles replied 6 months ago.

Ok, It looks like the 24V only goes to the starter and not the ignition switch. Can you verify this using a multimeter on the switch red connection? if so you could just use that switch to control the alarm that you want to install as well as the ignition.

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