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Author Topic: Control low voltage switch with arduino ?  (Read 553 times)
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Hello !
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I would like to command the switches on a hacked MP3 player with the arduino.
This player have a 1,5V battery.
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I tryed to use a 4N35 optocoupler, but this circuit doesnt'n works,
maybe the voltage or the current is very low and nothing happens.
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I search on the web for components, and I will try with a 4066, what do you think about that ?
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Overall, how to control low voltage (<5V) and low current circuits with the arduino ?
It's easy when the voltage is higher than 5V with transistors (2N2222, MJE3055, opto 4N35...)
but if is lower than 5V, I don't know ???
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Thank you very much for your replies, and excuse my bad english !
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Optocouplers or 4066 is a good option, when dealing with low vokltage switching.

Did you try to switch something else like a simple LED circuit to make sure the optocoupler works as it should ?
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Yes I tested all the optocouplers (4N35) with a "debug LED" and it works fine, but when I plug the MP3 switch it doesn't work.
if the 4066 is a good issue, I will buy it and if it work, I'll post a photo of my circuit.
Thank you for your reply !
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did you try changing polarity on the (mp3 player side) of the optocoupler?
you should find out what the buttons of the player actually do. that is, are they connected to ground or +whatever (probably 1.5V, maybe even more if the player uses a step-up converter).
if you can short the button with a wire, an optocoupler should do the trick. if the source is too weak to find its way through the opto's phototransistor maybe you can steal the current from somewhere else on the player's board?

best, kuk
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Hello !
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Yes I reversed the polarity on the MP3 side of the optocoupler but it still didn't work. The circuit of the MP3 is too tiny for me and I only plug the switches to my breadboard, i can't steal the current from another part of the MP3 !
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This week I will buy some components (4066 or another one ) to fix this problem.
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All the best, Alex
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Maybe use the optocoupler to switch a little reed relay?
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