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Author Topic: Arduino controlled telegraph sounder  (Read 479 times)
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Hey all,
I hope I'm posting this in the right section, and excuse any ignorant mistakes I have (or will) make, I'm new to this and trying to feel my way through.  I have an old western electric telegraph sounder that I would like to have controlled by my arduino uno.  I know I cannot drive it directly off of the digital pin as it pulls ~40mA, and the max on that pin is 20mA, iirc.  From the research that I have done, I believe what I need to do is separate it using a 2n2222 transistor and power it separately.  Is there anything else I would want to do in order to protect my board?  Any and all suggestions/information would be appreciated.  I searched and only found one other post mentioning a telegraph sounder and he was dealing with a dkuino board. 

Thanks,
Michael
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Inductive? Basically an electric bell?
If so I would tend to opto-issolate and use a separate supply.

circuit you can adapt here - Bottom of page

http://www2.mec.ua.pt/activities/graduationprojects/graduationprojectpages/2003-2004/H1/PICs/picbook/en/6_05Poglavlje.htm
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Is there an advantage to using an optocoupler as opposed to the transistor as well as a diode bridging the coil to deal with kickback?
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