Replacing Push-Button w Arduino

Using Arduino General Electronics
21

Yes

22

Good point to consider with this hack, but in this specific application, thereā€™s nearly zero chance of that occurring

23

  • The HS chip being powered by 12v probably is looking for a higher voltage ? :roll_eyes:

  • You are switching the HS input between 5v and ground, where the original circuit goes between 12v and open circuit, not sure what long term will show.

  • BTW, I too like using single gate chips.
    My often used chips.

    Gates
    Gates858Ɨ1834 227 KB

24

Looking at the schematic that you provided in post #13:
When you press any of the buttons, a current is going to flow through R1, turning on the PNP transistor.
This transistor seems to be switching power to the IC and the RF oscillator transistor.

When you just apply 5V to the pin of the IC, you are not switching on that transistor.
That may be detrimental.

Does the LED come on with the 'applying 5V to the IC pin' modification?

25

The schematic I posted in #13 is from the IC datsheet, not sure if it represents the actual PCB/remote Iā€™m hacking.

However, when Iā€™m applying 5V, both the LED indicator AND the remoteā€™s device both turn on. So itā€™s working (in the sense that the remote is sending its signal).

But assuming that schematic is how the remote is designed, my guess is that PNP transistor is for power-saving (so that the IC is only powered when a button is pressed). Then I donā€™t understand how itā€™s working off an external 5V trigger eitherā€¦.but it somehow is.

26

Or is it possible that the external 5V trigger is also triggering the base of the PNP, which then powers the rest of the remote (from the 12V)?

27

Sorry, I am new in the topic - why don't you want to use a most simple solution from the #7? It needs only two cheep elements and its influence to original schematic will be minimum

28

I donā€™t have an optocoupler on hand, and the one listed is $4 on Mouser (and Iā€™ve seen elsewhere that version isnā€™t intended to be used as a switch). 4$ isnā€™t exactly expensiveā€¦but are there less-expensive/equally-suitable options?

29

There are a lot optocouplers on the market, the one most common used is PC817 that costs a way less than listed above.
However, it is worth checking whether it is suitable for your case.

30

I have used these ones from Digikey, with an Arduino.https://www.digikey.com/en/products/detail/liteon/LTV-814H/385820

31

Would this also be suitable for my use:

32

The EL357N and PC817 have closely compareable specs, but i don't know much more than that.

33

  • If you can find these, H11F1M H11F2M H11F3M, they have many applications in your future projects too.

  • About $1.00 each on AliExpress.

Try lowering the R30, from 300k to say 1k.

IMG_3246
IMG_32462017Ɨ959 152 KB