Arduino controlled telegraph sounder

Using Arduino Motors, Mechanics, Power and CNC
1

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

2

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

3

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?