Do I have this correct?:

You need a normally open (NO) momentary switch for "On", a normally closed (NC) momentary switch for "Off", and a Bosch 0-332-204-150 relay.

On the relay:

Pin 30: Main Power In
Pin 87: Main Power Out
Pin 86: Switched Power (relay control)
Pin 85: Relay Ground

You wire up the relay so:

Pin 30 is connected to +12 that is switched by the ignition switch.

Pin 86 is connected to +12 that is switched by the ignition switch and has the NO momentary switch in-line.

Pin 87 (main power out) goes to the camera and is jumped to pin 86 (relay control).

Pin 85 is connected to ground and has the NC momentary switch in-line.

When you press the "On" momentary switch, the relay is energized and provides power to the camera and to its own coil so it stays "latched". Pressing the "Off" momentary switch removes ground from the relay coil and it disengages. If you turn the ignition switch off, the coil disengages since there is no power.

Correct?

Scott

Yep. FYI, not all part numbers come up easily in a google search. It's nice to provide a link if you have one. I finally found the pinout for the Bosch 0-332-204-150 here:

Not everybody would have taken the time to find that.

So here's the revised drawing as you plan to wire it:

NOTE: no polarity is provided for the coil, so pins 85 & 86 may need to be swapped if it doesn't work.

 

Hmmm. Seems like the switch needs to connect to the collector of Q3, not the base?

 

Afterthought:

Automotive topics are not permitted on this site. I helped because it is for an offroad vehicle, however I suspect the only reason the thread stayed open is because it flew under moderation's radar. In the future, if your topics are automotive related, it would be best not to explicitly state that. Or visit a forum in which automotive topics are not banned. Otherwise, we are happy to help with (almost) anything, so long as it isn't:

Any kind of over-unity devices and systems
Automotive modifications
Devices designed to electrocute or shock another person
LEDs to mains
Phone jammers
Rail guns and high-energy projectile devices
Transformer-less power supplies

 

Hmmm. Seems like the switch needs to connect to the collector of Q3, not the base?

oops... You are correct. My bad. I was just drawing it out of memory. Try this then...

 

oops... You are correct. My bad. I was just drawing it out of memory. Try this then...

how would he turn it off, other than by cutting ignition power?

 

how would he turn it off, other than by cutting ignition power?

Push the button...

I found the circuit here. It is another forum that I sometimes look through. There are a few other designs by some of the users there that basically do the same thing.

 

Actually I've been observing. The observation that it is for a vehicle that is not street legal is why this thread is still open is an accurate one, though I may have been lax.

Generally anything that is power by a cigarette lighter is also allowed, since this is not a modification.

 

i think a thyrister will do this job, a thyrister will turn if you put a positive voltage to the 'GATE' however if you remove the power source or turn it off... it will not turn on again untill you put a positive voltage to the gate.

 

Check out this switch I found:

http://www.pololu.com/catalog/product/750

It looks like it does exactly what I want and the price is right. What do you guys think?

Thanks,

Scott

 

oops... You are correct. My bad. I was just drawing it out of memory. Try this then...

Ahh but that circuit is great- it's BRAIN CANDY! I will use that on something for sure!

 

Check out this switch I found:

http://www.pololu.com/catalog/product/750

It looks like it does exactly what I want and the price is right. What do you guys think?

Thanks,

Scott

I have seen that one too and the circuit I showed is similar to this one. It should work for your application fine, just make certain to get the one that has the higher voltage range. It does take away some of the fun of building something yourself though...