Simulate button press with passive components?

[eevfan007]

Hi!

In my work with hacking a treadmill, I have soldered leads onto the buttons on the treadmill. By shorting the leads, the button is pressed, obviously.
When I control this through an arduino I use a 5v relay. But the "clicking-sound" from the relay annoys me, and I was thinking that the same must be possible through the use of transistors. Are there any added risk of connecting the leads between the collector and emitter, and just sending a small amount of current into the base of the transistor to have it "open/push the button".

Or would an opto-isolator work just as well maybe ?

[Rerouter]

it depends on what its driving, an optocoupler would be better

[Psi]

A reed-relay could be a good drop-in replacement and would work exactly the same as the existing relay except the noise would be so small i doubt you'd hear it.

Reed relays can't handle much current but the treadmill buttons are likely low current inputs to the treadmill mcu.
(i'd check that though)

[SeanB]

I had a lot of success using a CD4066 quad analogue switch. There is a video on the EEVBLOG channel about interfacing them as well.

[cwalex]

Hi!

In my work with hacking a treadmill, I have soldered leads onto the buttons on the treadmill. By shorting the leads, the button is pressed, obviously.
When I control this through an arduino I use a 5v relay. But the "clicking-sound" from the relay annoys me, and I was thinking that the same must be possible through the use of transistors. Are there any added risk of connecting the leads between the collector and emitter, and just sending a small amount of current into the base of the transistor to have it "open/push the button".

Or would an opto-isolator work just as well maybe ?

The most common button connection in electronics that I have come accross is a pullup resistor and the button pulls down to gnd. You could try just connecting one of the arduino digital pins to the treadmill where the button would connect and just set to low when you want to simulate button press.

[ivaylo]

Trying to make sense of the title here. Do you mean "passive" like a transistor, vs. "active" like a relay? Because none of the options you ask for involve passive elements, if you know what I mean...

[ivan747]

I think he meant discrete components. I'd go for the optocouplers or the reed relays. Remember to connect the optocoupler's transistor the right way round, so the current enters the collector and exits the emitter.

[cwalex]

if the arduino and the treadmill control board share a common ground then I don't know why you would need to add any extra components like relay or optocoupler to simulate button press unless you need some sort of isolation ??