I have an alarm clock that the alarm sound can be turned off if any button is pressed.
I would like to disable all the buttons and enable the buttons based on logic in my Arduino.
I'm trying to find what circuit or circuits I need to break on the clock in order to disable the buttons.
Once I figure that out, what will I use to break it? should I just use a few relays? or there's a better option out there?
Also, I don't like the clicking sound of relays
Any help will be appreciated
Start with your alarm clock, what's the model and manufacturer?
Alternatively, if you're having trouble with an alarm turning off too easy you can get a rolling alarm clock that won't turn off until you catch it.
I don't want to buy a ready-made solution, I want to make something my own
This is the clock that I have Amazon.com
But the question regarding breaking a circuit in an existing low voltage product is probably a general question
Is your intention to not allow any of the buttons to turn off the alarm sound until you enable it?
Without knowledge of how the circuit in the clock works, the only way is to switch off one of the wires to each button.
If all the switches have one side connected together, then you can stop them all with a single relay.
If you don't want to use relays, then the best would be opto-coupled FET's (AC type or wired correctly to be polarity insensitive).
The contacts of a relay or opto-fet are isolated and so don't care what the circuit looks like. You would simply wire a relay contact (Normally open) or the output of the opto-fet in series with one of the wires to each switch (or if the switches are on the pcb directly, you would need to cut the track to one side of each switch and wire the relay across the track that you have cut. Then you can control the functioning of the buttons with the Arduino.
If you intend to actually operate the clock functions that normally would be done by the manual buttons, then you would wire the relay contacts or opto-fet output across each of the switches.
I get that. I'm building a clock right now
But cutting a button off is more difficult than triggering a button.
It might be easier then to build the entire thing instead of modifying one.
Thank you daveve
You have me the answer I was looking for.
Do you think this part is a right fit for what I'm trying to do?
What do you mean by
AC type or wired correctly to be polarity insensitive?
Ok, so what I understand from your question you need the following to make a basic alarm clock:
To disable the clock, you can use a push-button, so that when the value of the push button goes high (pressed) the buzzer stops. This can be done through a while loop maybe.
You can also do the above with a app, so that when you click a button in the app the buzzer goes off.
Regarding @daveve's answer you need a opto-isolated relay like this:
Regards.
You can use a solid state relay to eliminate the click
What about the amazon part that I asked about before? Also whats the difference between that and a solid state relay?
Regular relay clicks
Solid state relay doesn't click
Nothing said about your Amazon part.
It's possible for someone with experience to do what you want to do but it's a lot harder to work your way though it with no experience, even with help from here.
That's why I suggested you build one from scratch as it will probably go faster and be exactly what you want rather than a half-hacked device.
@madd444 I agree that you can build it from scratch. I already told you the materials in my previous post.
See this for explanation of SSR:
The module you posted is an Optocoupler isolation board, which I don't know how to use. I'll see how it works and then tell you 
.
You can use a SSR instead of the electromechanical relay that I showed you in the previous post.
An SSR module looks something like this: https://images.app.goo.gl/3XoRT8iNfHZBcdKw6
Regards.
Hi mmadd444,
The one you have indicated is currently out of stock and also uses a transistor as an output.
What you are looking for is one with a mosfet output.
The reason for this is just that the mosfet acts in the same way as the contact on a relay.
Using a transistor output is possible, but you then need to do measurements on the circuit of the clock to see which way round the device must be and so is just more difficult.
An example of a opto-FET that will work is the TLP175.
This device is configured so that it is polarity insensitive by which I mean that you do not need to know which pin is positive and which is negative. Depending on the clock circuit, the one side of the switch will have a positive side and the other negative.
The opto-FET is a device which is just a low current solid state relay.
Sometimes opto-FETs are called solid state relays.
However, the name of "Solid state Relay" actually came into being when high current and high voltage devices were made. They are expensive and big.
So if you buy one of these, the will handle many amps and can switch the AC mains supply.
So not what you need for a clock run on batteries or a low voltage power supply.
You need something similar to the one you indicated on Amazon but with the correct output.
I will have a look to see if I can find a board available with the correct devices on it.
Wow, I could not find a board with the correct devices on it.
Although there are many ways to do what you wish, you need a little bit of electronic knowledge to use them.
You may need to go the relay route after all .....
I think he can buy those black colour SSR modules of which I showed a picture in post#12. That will work silently for switching purposes...
They are normally a bit BIG though for a battery clock - much bigger than relays.
They will work though.
Thanks @daveve
If I do test the current on the clock and connect them the right way, then the PC817 will do the job?
There is a possibility that the switches operate in a matrix - this means that the switches are connected between row and column lines to the clock chip - in this case the PC817 will not work.
If however, you find that there is a common connection to all of the switches and the other sides of the switches go off separately, then yes the PC817 will work if connected the right way around on each switch
I found a very nice solution- Transistors- the invention that changed electronics.
Transistors can be used as switches easily using Arduino Logic, small, silent and fast. Use a BJT / MOSFET depending on the voltage, current etc for your application.
Regards,
