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Home made LED fuse indicator


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9 hours ago, Fritz said:

Hi , 

Just made my self a simple LED fuse indicator so that i dont have to check on the inverter if all the PV's are connected and producing power.

What do you guys use?




please explain how you connect this to your PV?

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Indeed, I also cannot quite see it. Is it an NPN or PNP transistor. Why is the resistor not on the same side as the LED? What's the function of that diode, looks like a 1N4007?

Sent from my GT-I9195 using Tapatalk

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That is a very interesting circuit... I'm not to keen on it either because you have to take the positive lines on both sides of the fuse as well as the negative line to the circuit and it is polarity specific - if you want to monitor a fuse in a negative line, you'll have to use a NPN transistor and basically invert the circuit. Below are easier circuits for monitoring fuses in AC and DC circuits.

Fuse Monitor 2.jpg

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7 hours ago, Fritz said:

basis circuit that i got from internet, i just change the components to match my specification. ( voltage and current)




Okay, I see it. While the fuse is intact, the base of the PNP transistor is pulled up to the positive line (well, within about 0.7V of it). This is technically enough to turn a transistor on, but because the LED is on the emitter side that raises the emitter voltage by about the same amount so the transistor is off. When the fuse goes, R2 pulls the base down to ground and Q1 turns on. R1 limits the current into the LED.

For a 48V bank I'd use 6k8 for R1. I can't see in the picture what you used, though it looks like you used 27k for R2 (which is perfectly okay).

The idea I had in mind is closer to what @superdiy posted above. Just stick an LED across it. While the fuse is intact the voltage drop over the fuse isn't enough to bias the diodes (or the LED) forward, when the fuse goes... lighty lighty...

Edit: D1 is there to prevent the base of the transistor from being pulled down to ground via the load. I think. Because if that happens then the transistor goes boom.

Once again, Afrikaans is so beautiful in this regard. We don't bias a Transistor. Ons span hom voor.

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