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Author Topic: help connecting Arduino UNO to n-ch MOSFET via Optocoupler  (Read 7638 times)
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Thank you both! Please tell me if I put it right (I omitted the other two instances because I will solder each separately so that if there comes a need to add another solenoid I will just solder up another one):



Could you please tell me how to calculate the voltage at the gate? I was thinking, if I at any time later for any reason wish to use this driver for, example, 12 V motor, the gate voltage will also drop, yes? To about 5-6 V? This means I can only use 12 - 24 V motors here? How are drivers usually designed so that they can be used for as wide voltage range as possible? (I hope I am not asking too much).
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The 470uF andf 0.1uF capacitors are in the wrong place. They need to be connected directly across the 24V supply (but physically close to the mosfet). Otherwise, the schematic is OK.

Unless you are using fast PWM, the diodes in parallel with the solenoids do not need to be Schottky diodes - ordinary silicon rectifier diodes will do.
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You do draw your schematics in a very odd way.
I would connect those capacitors across the supply not the solenoid.

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if I at any time later for any reason wish to use this driver for, example, 12 V motor, the gate voltage will also drop, yes?
Yes.

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How are drivers usually designed so that they can be used for as wide voltage range as possible?
They are more complicated with a regulator giving you that extra voltage source you had in the first place.
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You do draw your schematics in a very odd way.

Yeah, its about time I read some tutorial on how to make schematics.

Anyways, I have read around a little bit, found out that multiple smaller caps are better than one big.

Also, if I leave the circuit online 24/7, the caps will be charged all the time even if they are only used for small fraction of that time. Will because of that their life expectancy be smaller? Should I add another FET that will block the entire power supply when its not needed? (sorry if the question sounds stupid, Im later planning on building a h-bridge and am accumulating knowledge for later also)

« Last Edit: February 09, 2013, 06:36:30 pm by Terraviper-5 » Logged

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There is nothing wrong with the capacitor values, it is just that you have them in the wrong place.
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You do draw your schematics in a very odd way.

Yeah, its about time I read some tutorial on how to make schematics.

Anyways, I have read around a little bit, found out that multiple smaller caps are better than one big.

Also, if I leave the circuit online 24/7, the caps will be charged all the time even if they are only used for small fraction of that time. Will because of that their life expectancy be smaller? Should I add another FET that will block the entire power supply when its not needed? (sorry if the question sounds stupid, Im later planning on building a h-bridge and am accumulating knowledge for later also)



That can be the case when the cap is being used to bypass noise to ground for sensitive loads, but your solenoid does not give a hoot about what little extra noise that smaller cap might be bypassing to ground. The big cap is just to have a little extra initial current available to drive the solenoid load on, in case the power supply is not a 'stiff' one. In simple passive loads like a solenoid you don't even require a regulated power supply, just filtered with enough current capacity to handle the solenoid load. But yes move the cap(s) to be across the PS +/-.

Lefty
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