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Topic: [Solved]What is wisdom: adding fuses to my project (Read 887 times) previous topic - next topic

sterretje

Sep 18, 2016, 12:17 pm Last Edit: Sep 21, 2016, 05:06 pm by sterretje Reason: Solved
I'm in the process of finalising my project consisting of an Uno and 4 PWM outputs for 2A led strips (using FQP30N06L logic level mosfets).

I'm using two 12V/5A power supplies (switch mode, they say) and the power distribution looks like
Code: [Select]

PS1 (+) --> fuse ---+---> Uno barrel
                    |
                    +---> Ledstrip 1 --> fuse --> fet (drain)
                    |
                    +---> Ledstrip 2 --> fuse --> fet (drain)

PS2 (+) --> fuse ---+---> Ledstrip 3 --> fuse --> fet (drain)
                    |
                    +---> Ledstrip 4 --> fuse --> fet (drain)

First question is where I place the fuses. Just one per power supply (5A) or one per ledstrip (2A) or both (as drawn)?

I do not care too much that the stuff blows up (I obviously will try to prevent this), but it must not catch a fire and burn the house down ;)

And the second question is if this requires 'fast' or 'slow' fuses.

Thanks for reading
If you understand an example, use it.
If you don't understand an example, don't use it.

Electronics engineer by trade, software engineer by profession. Trying to get back into electronics after 15 years absence.

Wawa

It could be that the switch-mode power supplies are already short-circuit protected.
Leo..

sterretje

Might be, but I can't find spec :( Sky 1205UV, similar to laptop power supplies. So that would mean a fuse at the power supply side.

Not sure if your reply implies anything regarding the fet side. Just to prevent overheating in case I try to push 5 amps through one fet.
If you understand an example, use it.
If you don't understand an example, don't use it.

Electronics engineer by trade, software engineer by profession. Trying to get back into electronics after 15 years absence.

Wawa

The only way to know if your supply is overcurrent protected is to test it.
A 6Amp load, e.g. a car headlightbulb would do.

But if you're that worried, then add an inline fuseholder with a fast-blow fuse to the +wire.
The fets at the end of the strip could live in a metal box.
Leo..

raschemmel

#4
Sep 19, 2016, 07:40 am Last Edit: Sep 21, 2016, 06:12 pm by raschemmel
Quote
I do not care too much that the stuff blows up (I obviously will try to prevent this), but it must not catch a fire and burn the house down  
Maybe you should look into the YG1006 FLAME SENSOR. It is available as a module. I breadboarded a discrete circuit of this sensor using this this circuit and it was very sensitive to the presence of a flame. Some smoke detectors has a Normally Open relay screw terminal pair on the back.
I use this at work to energize a 12V relay and use the Normally Closed contacts on the relay to supply AC power to power supplies. When the smoke detector is not detecting smoke the N.O. contacts are OPEN, so the 12V relay is OFF and the Normally Closed contacts on the 12V relay are CLOSED. When the smoke detector detects smoke , the 12V relay energizes (because the N.O. contacts separate the 12V dc supply from the relay coil) and the Normally Closed contacts of the 12V relay OPEN, removing power from the equipment in question. I have installed about 8 of these circuits in the lab directly above equipment that is on overnight. If there is smoke , the 277vac contactor will de-energize , removing power from that equipment. It has been tested after every installation .
I could see how the YG1006 flame sensor could be utilized in a similar fashion. (Using an analog input or a comparator)

Arduino UNOs, Pro-Minis, ATMega328, ATtiny85, LCDs, MCP4162, keypads,<br />DS18B20s,74c922,nRF24L01, RS232, SD card, RC fixed wing, quadcopter

sterretje

If you understand an example, use it.
If you don't understand an example, don't use it.

Electronics engineer by trade, software engineer by profession. Trying to get back into electronics after 15 years absence.

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