Great info by Crazy Steve and others. I have wired many cars and was in the Electrical trade for 44 years but still pick up a few things here. Just wired two OT 8 second drag cars for friends with lots of electrical gadgets. Both worked fine and no bugs to sort out. They are running today at Sacramento.
I want to run a 12 volt motor in both directions, works fine by switching polarity with jumpers. Is there a way to wire this two channel relay to do this? The 12 volt input is at left, and each channel has 3 terminals, NC, Common and NO. Each remote button actives a separate relay. I can't figure out how it would be wired, assuming it's possible.
If it was one button that operated both relays at the same time, you could do it with one more relay for turning the power on/off. Or if you could add two 3PDT relays (ice cubes), this could operate those relays and give you forward/off/reverse. But with just this, no.... The other concern I'd have is the motor size. Ice cube relays are generally only good to 10A max, that's pretty light for a motor load unless it's a pretty small motor (4A at full load or less). You could do this with 'standard' Bosch-style relays, but you'll need six of 'em....
Buy a winch relay set up to match your motor. They make a small, fairly cheap one for the 2500 lbs winches, and a larger, more expensive one for the larger winches. Then you can use that remote, we used similar set up for remote controlled winches. Bones
Thanks guys. Not a big motor, draws 4 amps under load. Bones, is this what you mean? I could then operate it with the remote thing above.
Yep, that'll work! Not being an off-road guy, never thought of one of these. Buy the smallest/cheapest one you can find, it will be plenty big enough for a small motor.
Looking for something similar to remotely operate the electric trunk lift linear actuator on my rod. Any suggestions? Phil
Thanks Pinball! I will wire up that way with a multimeter in place of the motor to make sure I have it right.
Phil, that set up will switch directions for most permanent magnetDC motors that you will find in the automotive area. Is that what you have/ need? Bones
Tested this with a meter in place of the motor and it works great (but you knew that). Now will this handle the current? Motor draws 4 amps, relays say 10 @30vdc. I'm also opening and closing a door so only going to run for 5-10 seconds. I suppose I'll put a 5 amp fuse in the + wire to the battery.
It will be fine, you're under both the amp and voltage ratings. See Steve's explanation in post #58. Chris
I've been using my remote very successfully as pinball diagrammed. Only problem is sometimes I forget the remote. So, I wired up dual position toggle switch on a seperate circuit to mount by the motor. Works great, except when I hook up both circuits. Somehow, I guess, when I hit the toggle switch it back feeds the juice going to the motor back into the relay board. How to get around this?
Lost track of this thread awhile back, but I think I'm caught up now. I'm about to do a complete wire job on my '37 Chevy, and came up with a very basic question. I grew up with cars that were generally wired like the upper diagram. But have noticed that many later vehicles use circuits like the lower one, that is switching the ground side as opposed to the 'hot' side of the load. My question is what are the benefits and negatives of doing it either way? I do understand electron flow and I can tell you a very long story about the little boy protons and little girl electrons which has an x-rated version. I'm just wondering why the car companies choose one method over the other.
I always put the ON-OFF switch between the battery and the load. If the ON-OFF switch is between the load and ground, the load is always "hot" (12 volts on the load device full time). There is always the chance of striking the load terminal and experiencing a little arc welding. Also, I can work on an electrical device without having to disconnect the battery.
Switching the load side is preferred, for multiple reasons. The main ones are ease of component replacement without disconnecting power and not having a uncontrolled circuit if a short in the switch leg occurs. But switching the ground is done occasionally for circuit simplicity; horn circuits are the most common example, where the horn ring on the steering wheel grounds to complete the circuit. On newer vehicles, it's usually done due to electronics, where switching a 'part' of a system is desired without interrupting power to the main part. Remember, the OEMs will do things that are compromises that may not be the 'best' choice if it saves them money. I used to have a neighbor who owned a late Caddy who was always after me to help him with electrical gremlins. This car had a 'variable ground' on the AC controls (a solid-state component that had 6-8 'grounds' attached to it, with a separate control circuit for the 'variation' part of it) that failed on a regular basis. He was too cheap to buy a service manual so I never did troubleshoot it and the part was NLA from Caddy. He bought every one he could find in boneyards (most of which didn't work) trying to get it to work... never did get it permanently fixed.
hmmmmm, if a short in the switch leg occurs, won't that have the same effect regardless of which side of the load the switch is on? I.e. a closed circuit
If the switch is before the load in the 12V feed, a short in the switchleg to ground will blow the fuse (or lacking a fuse, melt something).
Looks like your alternator is hooked up to the wrong side of the starter solenoid. Also your constant power. Bones
OK, this is true, IF a path to ground is established. When you posted "short in the switch leg" I assumed you meant a short that in effect closes the switch. Sorry, I misunderstood you.
I've seen both of Mark's cars running around to most meets in the local area. If they are wired incorrectly how can that be, or is the fire just a few more mikes down the road? I'm totally amazed that people can look at wiring diagrams and understand what is going on, or not. Bob
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