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I have an ATmega328 controlling a relay which is hooked up to a 12V horn capable of pulling 8A. I'd like to power both the horn and the ATmega328 using the same 12V 25-50C 1300 mAh battery. How can I do that? I have tried it in parallel and it works fine until the relay is closed. The horn will come on for a split second but then the ATmega loses power. What exactly is happening? Is the horn taking all the power, starving the ATmega?
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Sep 17, 2015 19:19
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| # ¿ May 20, 2024 08:32 |
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It's a SparkFun Beefcake Relay. It gets 5V straight from the voltage regulator, switched using a transistor. I'll have to try the capacitor tomorrow, the neighbours won't appreciate me firing up the horn at almost 10PM.
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Sep 17, 2015 21:49
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It wasn't the relay sucking up the current, it was the horn. The circuit worked fine without the horn connected. Anyway, I added a capacitor and all is well. Thanks.
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Sep 18, 2015 16:59
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I'm looking for some advice/sanity-checking on my first "proper" electronics project (proper in the sense that I'm trying to make it look professional). I'm a software guy by profession with experience in mechanical engineering, but electronics-wise just some small Arduino stuff making basic circuits on breadboards. I'm sick of using my phone as my bedroom alarm clock so I'm working on creating a small wooden alarm clock. What I'm planning so far:
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Jan 26, 2020 18:55
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KnifeWrench posted:I would never trust my alarm to something that isn't plugged into the wall, sleep mode notwithstanding. Is there a reason you're trying to make this battery operated? A simple wall wart could obviate all of your power concerns, at least for your initial prototype. As figured out, the flipping design is what was driving me to a battery powered device rather than a wired one where the cable would get twisted. I could use some sort of circular connector like a barrel jack that can spin when plugged in maybe? Something fancier like a slip ring as mentioned seems like it's getting pretty complicated for what I was imagining. As long as the battery in this thing can last a reasonable amount of time (a week, minimum) and I can give some indication that the battery is low (less than 24 hours remaining I guess), I'm pretty OK with using a battery powered alarm clock. csammis posted:The MSP430 by Texas Instruments is the MCU I use in power-sipping applications because of its extremely low current sleep states. Even the little ones would be able to handle your IO requirements without a problem. Ah you're right, I didn't mention the piezo buzzer I was planning on using. I'd like the LEDs to be on all the time. Would using PWM or something to have them very rapidly blinking so that it's imperceptible unless you wave the clock around save me significant power? It will be a 24 hour display. The 1000mAh source is maybe on the low side. The idea behind high capacity rechargeable AAs instead would mean that should the batteries get low, I can swap them out instantly rather than having to plug it in and avoid the cable problem.
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Jan 26, 2020 19:56
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