i thought about using a transistor instead. I hoped that I could bypass the switch with a transistor ? Is that possible ?
Yes it is but you need to know what voltage the switch has on it. As it is a radio it is very unlikely to be 5V. The point about using a PNP transistor as a top switch like this, is that the signal you put on the base of the transistor needs to be as big as the voltage you are switching. If it is not then then you need another transistor, an NPN one to boost the 5V signal from the Arduino to the voltage you are trying to switch.
Check out these relays. There are plenty with low coil currents that an Arduino could drive directly, and are quite small in size as well. Then you can complete a simple button closure and not have to worry about odd voltages or getting ground connected to the right place, etc.http://www.digikey.com/products/en/relays/signal-relays-up-to-2-amps/189?k=relay&k=&pkeyword=relay&pv72=1&FV=fff40010%2Cfff80368%2Ca8c0007%2C16040020%2C1f140000%2Cffe000bd%2C1140050&mnonly=0&newproducts=0&ColumnSort=0&page=1&stock=1&quantity=0&ptm=0&fid=0&pageSize=25
Thanks for explaining. But are you even sure the switch pulls a line high? It's common pratice to pull a line low to activate the switch.And if that's all that the Arduino needs to do you can probably do it without an Arduino with just a capacitor over the switch You then create a simple RC time delay
o if I want to switch a positive voltage I have to use a PNP transistor ?
Can the Arduino Nano even give 5,6v?
I'm not that sure the switch pulls it high. The voltage you measure on one side can just be the voltage because of a pull up resistor and the switch pulls that low. Then trying to switch the 0V to Vcc will just short the device You measured both sides so you had a reference point somewhere so I guess you found the GND of the circuit? Can you use the continuity test between the GND and the 0V side of the switch?
Can have multiple reasons. Two I can think of 1) That's the voltage that the controller (being it a ASIC or a uC) is run at 2) The pull resistors are under software control so they might be off when the device is off.And there is no guarantee both switches switch in the same manner. So focus on one at a time and I assume focusing on the power switch makes more sense.And it might even be a switch (or both) is (/are) multiplexed. Which makes it harder to measure.Two things you can check for the power button. - Can you trace where that 5,6V is coming from?- What voltage do you see when the power button is pressed?Assuming you found the GND of the device. (Did you? Are you sure? Why are you sure?)Because before knowing exactly how the switches are wired the only safe option is to bridge the switch with a relay. Other options can damage the device (or may not work or work, but the damaging part is the tricky bit ).
I want a PNP transistor who just works like the TIP120 but is activated by negative voltage and can switch on and off positive voltage. What do you recommend ?