Hello! I am currently using a ESP8266 ESP12-F module, everything works but I am stuck on thinking how could I simulate a button press, the original circuit has a button which has to be pressed twice for triggering a function, I looked around and found some relays which could do the job, according to my tests the circuit that needs to be closed is a non-voltage circuit (it accepts max 1V according to the manual of the machine, which has to be shorted to a gnd), the relay I found could have done the job however it says that can last up to 100000 times, I need my circuit to close and open twice around every two seconds for more than 16 hours a day, it's more than half the counts that relay could take in a single day, I still have to code and buy the double-circuit-close components, I thought making like a high-low-high-low code using a GPIO pin but I'm worried about how can much the board can last and if emits voltage, I'm still new to this and I thought maybe some transistors could do the job, however i'm not sure which one could suite this need, preferably some component which could do the double reset (high-low-high-low) in less than 50/100ms, could someone clarify this out?
TL;DR: I'm not sure which transistor/relay could close a circuit like a button does, it should not have any voltage and it should be closing the circuit every 50/100ms (lower is also fine) for a long period of time
Possibly. But some more important measurements needs to be made.
You say that the voltage is low. I assume you measured this across the button terminals/pins when the button is not pushed?
Is one of the button terminals/pins connected to ground on the device? Can you find a point on the device's PCB which is definitely ground and check continuity between that point and each of the button's pins?
How much current flows when the button is pressed? I would expect it to be very low, a few mA at most, but it's always better to check first before you decide what to connect to it. To measure this, use your multimeter on high current range and use the probes to short the button pins, simulating the button being pressed. If the teaching is zero, switch to a lower current range.
Hello, and no I haven't measured the outputs of the machine, I only referenced what the manual says, according to its manual it's a 1v max if the button is pressed, and a off current of 0.6mA maximum, with a short circuit current of 2mA, this has to be shorted to a gnd of the machine, here's a photo of the circuit behind this "no voltage circuit" (sorry I don't know how to attach a image from mobile): https://i.imgur.com/NIB8whv.jpg
Thanks, all good points. Now we have more information:
@foge thank you for the schematic. That is what my mind leapt to, insofar as it can anymore leap, from your description.
And… the good news is that either my or the other circuit is suitable.
Any small signal NPN transistor will work. The BC547 is fine.
The transistor should last forever, approximately, and is way fast enough.
A HIGH on the Arduino output pin will be the same as closing relay contacts or a switch connected at that point.
Common ground. If you have any need or reason for an isolated ground, then use the optoisolator.
Never heard of such an interface being called "no voltage", they just mean I guess don't be putting any voltage on in there. The transistor as a switch will not.
