Master blown fuse indicator

Thread Starter

planenuts

Joined Nov 28, 2009
9
OK, a caveat. This circuit has not been tested in a high electrical noise, vehicular environment. SCRs can be triggered on by noise spikes in an electrical system.

Hi Ken,

Understood.

I'm OK with it because it is not an integral part of any circuit on board. If an SCR or OI fails in any way, the fuse condition LED indicators still function as they have a hard wire path that will not be interrupted. If I get nuisance trips of the blinking LED with no corresponding blown fuse indication, I'll just ignore it and I may put a defeat switch into the circuit for that eventuality.

Re Aerolectric Connection warranty, I like that too. I've seen others by people offering parts etc for aircraft, that state flat out that using their part "will probably kill you".;)
I like the Homebuilt Aircraft community and ones like AllAboutCircuits because people generally take responsibility for themselves and enjoy learning new stuff. No one trying to hang a leaky hat on me.

John
 

BillB3857

Joined Feb 28, 2009
2,570
Check out the 4N39 device. It is an optically triggered SCR and may simplify your system as long as you are only driving indicators. Another thought...... If you are using an LED with a built in blinker, you may want to put a shunt resistor across it that will allow minimum holding current for the SCR. Some of those blinker LEDs pull very low current while blinked off.
 

KMoffett

Joined Dec 19, 2007
2,918
The 4N39 won't work in my circuit. You need the transistor output (originally a switch) to hold the indicating LED on after the SCR is reset. You may be right about the blinking LED. That's the case with the electromechanical buzzer.

Ken
 
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