Electronics > Beginners
What to do when your power source is higher than your power requirements
Explodey:
Hi folks -- super basic question here: I'm building a little project that just uses two of these little amplifier boards https://ebay.us/kPrc8I . Due to space limitations, I want to use a 9V battery, but the specs say that the maximum power requirement is 5.5V. In the past, I've used these eboot step down modules for this kind of stuff https://ebay.us/WBdBOR , but I'm trying to keep this as simple as possible and I'd rather not add another board if possible. So I'm wondering if it could be as simple as just putting in a resistor with the right value between the power and the boards. Would that work? I don't want to burn out my amp boards. Thanks!
rx8pilot:
You have a voltage that is higher than the requirement. The power is a different thing - voltage x current(amps).
You likely need a buck converter or linear regulator which can take a DC power source at a certain voltage down to a lower voltage. Resistors will NOT work with an amplifier board at all.
EDIT: That board definitely needs a stable-regulated power source. A switching DC-DC converter is the best option for battery power efficiency, linear regulators are best for low noise in amplifier applications.
Explodey:
I had a feeling that my question would betray a fundamental misunderstanding of the problem! :P I think I'll try to make space for AAA batteries.
Thanks for your reply.
rx8pilot:
--- Quote from: Explodey on August 21, 2018, 11:33:28 pm ---I had a feeling that my question would betray a fundamental misunderstanding of the problem! :P I think I'll try to make space for AAA batteries.
Thanks for your reply.
--- End quote ---
I have not studied your target amplifier PCB, but in general, amplifiers need a regulated power source to meet specifications. Batteries are not regulated. It may not be much of a problem in your case, but worth mentioning.
Audioguru:
Are your speakers 4 ohms or 8 ohms?
Four alkaline batteries in series produce about 6.6V when new which is too high. Three batteries produce 5V when new.
Three batteries produce 3V when ready for replacement but then the max output power is very low.
The max undistorted output power with a 5V supply and 4 ohm speakers is 2.2W so if each channel is blasting 2.2W then the power from the battery is 4.8W. The max current is 1.2A. Three new AAA or AA alkaline batteries cannot produce 1.2A. An ordinary 9V alkaline battery cannot produce even 0.4A. A resistor in series will increase the voltage and blow out the amplifiers when the output power is low and it will blow out your hearing with severe distortion when the output power is high.
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