switching a non logic level mosfet with arduino - Page 1
Forum section: electronics / general

author: m3vuv
author_rank: Super Contributor
timestamp: November 09, 2019, 12:35:28 pm
content: Hi,can anyone point me to a schematic to switch a non logic level mosfet with an arduino thats non inverting?,i have 2n3906 and 3904 trannys and some tip 29 trannys,ive no opto couplers,i see lots of schematics on the net,they all apear to invert the signal,its for low side switching a motor,the mosfet i want to use is a IRF 3205 cheers Paul m3vuv.

author: m3vuv
author_rank: Super Contributor
timestamp: November 09, 2019, 04:52:51 pm
content: i gather all you supposed micro controller experts dont know then!!

author: martinayotte
author_rank: Regular Contributor
timestamp: November 09, 2019, 05:23:33 pm
content: I think your question is not clear enough ...First, why you don't wish to drive the motor from low side directly ?The IRF3205 is a N-MOSFET, so it is for low side driving.For high side driving, you need a P-MOSFET where it gate is driven by another N-MOSFET to be able to drive it from low voltage MCU, so adding more complexity ...

author: oPossum
author_rank: Super Contributor
timestamp: November 09, 2019, 05:23:33 pm
content: https://www.microchip.com/wwwproducts/en/TC1427

author: m3vuv
author_rank: Super Contributor
timestamp: November 09, 2019, 07:51:23 pm
content: I balled up,it is for low side switching,the issue is the arduino not supplying enough volts to switch it fully on,it works but gets too hot! due to it not beeing fully on.

author: m3vuv
author_rank: Super Contributor
timestamp: November 09, 2019, 07:55:00 pm
content: your all missing the whole point,i want to do it with what i have,im suprised none of you can give a decent answer to my question!!,beggars belife!!

author: T3sl4co1l
author_rank: Super Contributor
timestamp: November 09, 2019, 08:04:01 pm
content: Can't wait four hours at a forum where a question might go unanswered for days? Beggars indeed...Would also be inclined to question whether you really need a transistor that fuckoff massive. It's tempting to use the least Rds(on) one can find, but it often invites problems that the average Arduino enthusiast likely isn't aware of.But if it's what was on hand, sometimes that happens.Y'haven't searched around for discrete transistor gate drive circuits? We had a good thread here a few months ago.Tim

author: madires
author_rank: Super Contributor
timestamp: November 09, 2019, 08:04:49 pm
content: You can use your BJTs to build a totem pole driver for the n-channel MOSFET.

author: cv007
author_rank: Frequent Contributor
timestamp: November 09, 2019, 08:09:43 pm
content: >im suprised none of you can give a decent answerMaybe they have better things to do today.I'll post something, if incorrect that will bring them out. There are things better, but this could probably make you happy enough.Second one probably better, as you may have the 12v but may not have the 5v, which would turn on the device. If the switch is using the same supply, then if there is power for the device, there is power for the switching transistor to turn off the mosfet by default. A pin is high impedance by default so will take an active piece of code to make the pin low and turn on the mosfet via the npn.Or something like that.You should get some kind of simulator software so you can try things out, and not have to always rely on others. Others can point in directions, and can be useful, but ultimately its better to learn to fish than be handed fish.

author: Bassman59
author_rank: Super Contributor
timestamp: November 09, 2019, 08:18:54 pm
content: Quote from: m3vuv on November 09, 2019, 04:52:51 pmI do know. But you didn't say the magic words.

author: m3vuv
author_rank: Super Contributor
timestamp: November 09, 2019, 11:03:51 pm
content: well ive salvaged some d472 fets from a motherboar,see attached,do you think these will work at logic levels,ie will the arduino have enough volts on the digital pins to turn them on?,im planning on using 4 to drive a unipolar stepper.,thanks in advance Paul m3vuv.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: November 09, 2019, 11:17:20 pm
content: Yeah, that'll work. Not much voltage though. You'll have to supply the stepper with much less than 12V.Tim

author: m3vuv
author_rank: Super Contributor
timestamp: November 09, 2019, 11:52:57 pm
content: Its for a coil winder,i have a wantai 57by gh420 hybrid stepper,im going to try them on a 12v supply,speed isnt an issue,just need to wind a hv hv coil on my tek scope,its like 2000 turns needed,hence the reason for the project!.

author: Someone
author_rank: Super Contributor
timestamp: November 10, 2019, 02:01:40 am
content: Quote from: cv007 on November 09, 2019, 08:09:43 pmOr not feed a user who demands hand holding through every little step and won't make any effort to do their own research.

author: m3vuv
author_rank: Super Contributor
timestamp: November 10, 2019, 02:06:55 am
content: looks like ive sorted it using the fets i took off of an old motherboard,ther driving a 21 watt bulb via the arduino with out getting hot,thats using a 1k between the gate and ground as well to bleed the cap charge on the gate,there turning on and off fine and running cool.,cheers all.

author: cv007
author_rank: Frequent Contributor
timestamp: November 10, 2019, 02:42:12 am
content: I guess most have already figured out answering some of these questions is mostly a waste of time. I should know better by now, but apparently do not.

author: mikerj
author_rank: Super Contributor
timestamp: November 10, 2019, 04:23:23 pm
content: Quote from: m3vuv on November 09, 2019, 07:55:00 pmThis isn't the first time you've had a meltdown because a question hasn't been answered to your satisfaction within some undefined timescale. I suggest you demand a full refund and leave, I'm sure we will manage to cope without you.

author: madires
author_rank: Super Contributor
timestamp: November 10, 2019, 05:31:44 pm
content: Isn't this amazing? The OP even gets free advice on improving his soft skills.

author: m3vuv
author_rank: Super Contributor
timestamp: November 11, 2019, 02:12:55 am
content: I get anoyed to say the least when ppl come and reply with something totaly not was asked for,half just come out with crap not relevant to original question asked,it wastes everyones time,if i post i try and answer what the op is asking not come out with a load of horseshit to try and look clever!!.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: November 11, 2019, 06:07:20 am
content: You get what you pay for. I'll happily accept donations in exchange for carefully thought-out answers; my Paypal is on my website under Contact.Tim

author: magic
author_rank: Super Contributor
timestamp: November 11, 2019, 07:37:01 am
content: If switching speed isn't critical you could perhaps use a voltage multiplierBut I'm not sure how to turn it off then without using another GPIO.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: November 11, 2019, 08:44:15 pm
content: A charge pump driven by a pin is not a bad idea, for slow switching applications. Believe it's been discussed here before, among other unconventional GPIO applications. A potentially nice part about it, it's it's own watchdog timer of sorts -- if the CPU stops toggling the pin, it simply turns off. It only stays on while toggling.Tim

author: james_s
author_rank: Super Contributor
timestamp: November 11, 2019, 08:57:06 pm
content: Quote from: m3vuv on November 11, 2019, 02:12:55 amYou'd probably get a lot more helpful advice if you were to lose the attitude and gain some patience. We're not your personal engineering assistants, we're forum members just like you, and most of us have day jobs. You posted a vague question then came back with a rude reply only a few hours later. How can you expect such a quick response? What have you contributed recently? Post a clear question and then be patient and be polite. Likely quite a few people could give you an answer if they were motivated to do so but I'm not sure why anyone would bother to help someone who is being an ass.

author: oPossum
author_rank: Super Contributor
timestamp: November 12, 2019, 01:20:32 am
content: This is a charge pump design I used for driving IR LEDs with bursts of 30 to 60 kHz. Worked well for it's intended use.