Digital to Analogue

cletus

Hi folks, hope this is the correct forum. I'm just wondering if its possible to replace the digital buttons in the attached image with a toggle switch like that below. I only want to be able to select two of the five inputs (why is a slightly long, and probably slightly more ridiculous story. Suffice to say I can't leave things alone)

Anyway, given that I want to be able to select just two of the available inputs, is this DIYable

ShRT

Judging by the pic, the buttons will be momentary i.e. only closed for the duration you are pushing down. The toggle switch you have above is not though.

As a simplest replacement, you could use this kind of toggle switch. The existing switches are most likely of the pad type so you will need to solder wires to the pads and then back to the toggle.
https://www.sparkfun.com/products/10545

This describes a method to use your original toggle in a momentary fashion:
http://www.simprojects.nl/toggle_to_momentary.htm

You could also do something with a microcontroller (arduino, pic, msp430 etc)

Find an old remote control to hack, all you need is two buttons. Remove battery.



Pick two buttons any buttons. Cut the PCB tracks to the chosen buttons and isolate from the remote PCB. Solder the designated remote control switch traces to the hifi switches on 4 core cable.
Presto wired remote.

cletus

ShRT wrote: »

Judging by the pic, the buttons will be momentary i.e. only closed for the duration you are pushing down. The toggle switch you have above is not though.

As a simplest replacement, you could use this kind of toggle switch. The existing switches are most likely of the pad type so you will need to solder wires to the pads and then back to the toggle.
https://www.sparkfun.com/products/10545

This describes a method to use your original toggle in a momentary fashion:
http://www.simprojects.nl/toggle_to_momentary.htm

You could also do something with a microcontroller (arduino, pic, msp430 etc)

Thanks for this reply. I have a couple of questions which may sound stupid but if you could bear with me. The buttons above would a appear to be momentary switches as you described. However once they have been pressed the selection remains u until another is made. Would the momentary toggle switch do the same, or will the selection hold only as long as the toggle is in the correct position.

The reason I thought the original toggle would work was that even if you maintain pressure on the momentary switch, the selection can still be used, ie if I stand with my finger on phono, the record player will still work.

@sir liamalot: I kind of need to have the toggle switch rather than more push buttons, but thanks for the suggestion. I have the remote that came with the stereo, and may find some other reason to play around with it

Has the stereo always been like that?
The selection would only hold as long as the button is pressed on a momentary switch, it'd be a like for like replace, in which case you may be better off with a rocker type switch or perhaps there's a fault with the stereo.

cletus

I may not be explaining myself accurately. I suppose following on from shRT's post, i am trying to establish the likelyhood of them being momentary switches. Having looked further at these, it would appear that a momentary switch will activate and de-activate.

The selector buttons above, once pressed, will stay on that selection (an led in the button lights to indicate which input is in use) until another selection is made.

In your opinion, sir liamalot, would these likely be momentary switches?


My point about holding down the button was not that this was neceassary for operation, rather that, if it was a momentary switch, it still worked while being continously depressed, so would there be an issue with the toggle switch continously "depressing" the conection.

Hope this is a little clearer, thanks for the help so far

The original panel is most likely a soft latching transistor circuit implementing momentary switches.

A momentary switch itself holds nothing it's designed as a pulse connect.

I'd be pretty confident the originals are momentary much like the design of the remote I posted.
If you observe the two "S" traces (button pads) on the PCB I posted these are two sides of a switch the conductive carbon on the rearside of the button momentarily makes the switch. I'd expect the stereo to be the same with tack switches.



You'd just be adding another momentary switch in parallel.
If you added a rocker type switch it would do the same thing you're just holding the gate of (probably) a mosfet high which is unnecessary.

Not a thing I could say for certain without seeing it's gubbins though.

cletus

Then the gubbins you shall see, sir

I had come across soft latch button on my admittedly half arsed research. So a momentary toggle switch, or the diy version would work?

To explain a little further, the internals of the stereo will be removed, and placed in a different housing, as a result the buttons will no longer fit, so i want to solder in a new selector switch, and the toggle is most aesthetically pleasing to me

Yeah as long as you keep all the bits connected as they were should be fine, watch out for big caps holding charge and all that lark.

All you are doing is adding a parallel switch so it's either = on.

If you find a tack switch under the buttons stick a DMM on the feet and see (usually they're two for input, two output) if you get continuity across the switch only when it's pressed it's momentary.

Problem with toggle switches is bounce...it may not be an issue, the circuit is designed slow response because fingers are not as speedy as electrons.

Watch out for parallel ins and outs (note the switch might be mounted 90° offset to that diagram...but you get the idea)

cletus

http://www.maplin.co.uk/p/10a-toggle-switch-dpdt-momentary-on-off-on-n41kr

So I found the above in maplins. I presume if I want two switches running to the one toggle switch, it'll need to have four pins rather than just two

2 pins = 1 switch
4 pins = 2 switches
6 pins = 4 switches, centre common

cletus

Sir Liamalot wrote: »

2 pins = 1 switch
4 pins = 2 switches
6 pins = 4 switches, centre common

4 pin it is so

You don't need 10amps (500mA is loads)
http://www.maplin.co.uk/p/sub-miniature-toggle-switch-h-momentary-on-off-on-dpdt-fh07h

Make sure it's DPDT (double pole, double throw; 6 pin) or SPDT if you want to complicate things (single pole double throw: 3 pin). 4 pins could be DPST.

I'd go for 6 pins...same price, don't wire the pins you're not using.