Author Topic: Simulate button press with passive components?  (Read 4316 times)

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Offline eevfan007

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Simulate button press with passive components?
« on: January 27, 2014, 08:23:08 pm »
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 ?

« Last Edit: January 27, 2014, 08:27:13 pm by eevfan007 »
 

Online Rerouter

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Re: Simulate button press with passive components?
« Reply #1 on: January 27, 2014, 08:38:58 pm »
it depends on what its driving, an optocoupler would be better
« Last Edit: January 27, 2014, 08:40:49 pm by Rerouter »
 

Offline Psi

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Re: Simulate button press with passive components?
« Reply #2 on: January 27, 2014, 08:45:20 pm »
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)
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Offline SeanB

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Re: Simulate button press with passive components?
« Reply #3 on: January 28, 2014, 05:46:04 am »
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.
 

Offline cwalex

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Re: Simulate button press with passive components?
« Reply #4 on: January 28, 2014, 12:29:24 pm »
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.
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Offline ivaylo

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Re: Simulate button press with passive components?
« Reply #5 on: January 28, 2014, 07:59:51 pm »
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...
 

Offline ivan747

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Re: Simulate button press with passive components?
« Reply #6 on: January 29, 2014, 02:47:28 am »
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.
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Offline cwalex

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Re: Simulate button press with passive components?
« Reply #7 on: January 29, 2014, 10:10:27 am »
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 ??
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