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Circuit

P

PeterT

Ultra Member
Premium Member
Ok, this should provide lots of comedic entertainment to electrical savvy guys. Apparently I am not qualified on the most basic of circuits.
This is my glow plug ignitor box work in progress & mockup strip holding 5 glow plugs. I have 5 voltage regulators in parallel & switch dedicated to each plug (at least that was my intent).
The red wire from regulator is connected to glow plug stem. Stem is insulated from body, goes to glow coil. The plug body/threads/aluminum dummy strip are ground.

The issue is when I flick a switch, they all light up. WTF? At least the magic smoke stayed in :/
 

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Your grounds probabaly (should be) connected together somewhere. Switch the hot, not the ground
 
Not sure if I'm using 'ground' word properly but maybe this helps explain.
When you say move the switch, like so?
 

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Yes move the switch to the positive line (red), I'm out atm, but I'll explain in 20min when I get home
 
@jcdammeyer has got it for you

how you had it when you switched one regulator on you were completing the ground circuit for every regulator, as the grounds are all tied together after your switches, including everything on all of the boards, so power was able to flow through your switch to every ground, and back to the battery through the positive's as they were already connected to positive

as a general rule in dc circuits you typically switch the positive as grounds are generally tied together
 
Thanks guys. I actually started out the way you show with switch between regulator & glow plug. But when I tested a single module, I noticed a little LED light came on inside the reg when I first connected the battery but not yet the glow plug. Because the glow plugs are only one for say 30 secs to start the engine, then off for say 10 min while running, I wasn't sure if it was good for the regs to be 'on' for this duration. Not really sure if it hurts them or draws much power but that's why I put it on the 'in' side so reg would see now power at all. Is this still an option & I just happened to pick the wrong wire for the switch?

1667699979245.webp
 
PeterT said:
Thanks guys. I actually started out the way you show with switch between regulator & glow plug. But when I tested a single module, I noticed a little LED light came on inside the reg when I first connected the battery but not yet the glow plug. Because the glow plugs are only one for say 30 secs to start the engine, then off for say 10 min while running, I wasn't sure if it was good for the regs to be 'on' for this duration. Not really sure if it hurts them or draws much power but that's why I put it on the 'in' side so reg would see now power at all. Is this still an option & I just happened to pick the wrong wire for the switch?

View attachment 27675
Click to expand...
Just move the switches so they break the green trace instead of the red trace. As @phaxtris mentioned since the grounds and the outsides of the glo plugs are common (often called ground) you don't want to switch those.

Like this:
 

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phaxtris said:
Your grounds probabaly (should be) connected together somewhere. Switch the hot, not the ground
Click to expand...

Maybe you saying this, if red OUT is hot to the plug, then red IN is likely hot & thats where I should have put the switch?
 

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PeterT said:
Maybe you saying this, if red OUT is hot to the plug, then red IN is likely hot & thats where I should have put the switch?
Click to expand...

exactly, well sort of....electrons actually flow from negative to positive, but the way dc circuits are designed the common/ground/negative/black is typically tied together so the control is with the positive/hot wire, not with the ground/neg/common/black......at least in basic circuits

and you are right, you would want the switch in positive before the regulators in a battery application...it wont hurt the regulators, but there will be some small current draw wich could eventually drain the battery
 
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