I have resisted as long as I can to post and ask for help. I'm too much of an anal-a-techie to just accept a circuit, or to assume that it will work based on all the searching I've done.
I'm working on a simple stateful audio channel selector.
My design would ideally use three proximity sensors inductive or capacitive to sense a selection of a given input stereo channel (1 of 3), then using a DPST relay for each channel, I'd connect the appropriate L and R channels up to the output.
Currently I have a working prototype where there are 3 physical switches (simulating the prox sensors) raising inputs on the arduino to HIGH, then a simple control program to raise the relevant output line to HIGH. Currently the 3 channels of outputs are indicated by a LED, but would be the coil of the relay.
Phew. After that, my questions are relatively simple (I hope).
Can you recommend a DPST 5v relay that I can use with the playground example (relays.pdf), assuming here that I'd still get away with using the arduino's 5v, a 2N2222 transistor and a 1N4004 Diode, as per the diagram?
NOTE: The out on the relay will be connecting non-amplified audio from various line out sources to the line in on some powered amplified speakers.
I've struggled to find any examples of how to implement the proximity sensors. I'm also a little unsure of which would be best suited as a cost / benefit ratio. I'm essentially wanting to mount them under some thin perspex and to react to a nearby finger
Any help on this one would be greatly appreciated.
Thanks for the reply. Unfortunately that doesn't help massively.
I've checked out the UK Omron website and they don't seem to even manufacture an equivalent signal DPST relay. The link was to a DPDT, which isn't what I'm after...
I saw the post on the arduCapSense shield, but again, not what I'm after. I need (correct me if I'm wrong) an induction based sensor if I'm to mount it UNDER some 2mm perspex and get the input from it.
Something like this http://is.gd/kc1CK looks promising, but I'm a complete noob and if it internet isn't too forthcoming with answers, I'm a little stuck.
Deviruchi, if all that you wish to do is route low amplitiude audio signals under control of an Arduino board, and audio quality is not Audiophile, rather than using relays drive transistors and catch-diodes and such, consider instead using an arcane CMOS device such as the 74HC4051. Or perhaps the 74HC4066. Look up their data sheets, these devices are cheap, widely available, and easily interfaced with any Arduino project.
...consider instead using an arcane CMOS device such as the 74HC4051
Excellent, DHM! That looks to be precisely what I need. Looking at the configurations, I need a HC4052 - that has the right number of channels and more than enough inputs.
I assume that the pinout HIGH on the arduino will trigger the high on the CMOS?
I'm learning as I go having only done an AS level in electronics over 15 years ago where I learned nothing - I'm much more at home with a C compiler
For parts in the UK...
Good stuff - I'll keep it bookmarked. There's a small home-run business nearby where I live that sells components for when I need less than 20 of something
For finger sensing...
I'll take a look, thanks tkbyd. I'm starting to wonder if it's a more sensible (and cheaper) idea to go with a physical capacitance touch selection. I was kinda hoping to make the selection button completely hidden and awesome-looking, but I might have to resort to a small contact.
Out of interest, does anyone know how monitors / TVs typically do that? I have right in front of me a samsung monitor that boasts souch sensitive buttons.
Thanks for your help guys - I appreciate the effort in helping a noob
Richard - I'll look into that, thanks. It would be good to get away with this as a cheap alternative.
DHM - I bought a HC4052 (datasheet: ST Microelectronics 446419, DS datasheet pdf) but I'm having trouble with what I would expect, and what is happening. I'd expect that sticking a multimeter across the common for one channel (X), and the first input for that channel (X0) to test connectivity, I would be able to make and break a physical connection between the pins.
Possible niaively I assumed that was how it all worked.
Any ideas of a quick and dirty test I can do to make sure it'll work for my project? The datasheet doesn't give me too much of a clue.
Noob question (sorry):
VCC and VEE confuse me slightly. I'm currently assuming that VCC is simply the input power, but the datasheet says that VEE is used to make the mux/demux digital. Am I right in thinking that just VCC and GND are required?
I know that things like the above have been around for years, and DO WORK.. but they've always seemed a little round-about to me. Maybe I just like doing things the hard way.
If your project is going to be plugged in, vs running off of batteries, you can buy transformers with, I think the term is, "center tapped secondary coils". They give you a positive and a negative low voltage from the high voltage fed in. Then it's just a matter of simple rectification and regulation.
If you don't want to build your own two rail supply, power supplies for computers... and by this I mean the "big" units inside desktops, not the "wall warts" common for laptops, also have negative voltages you can use. You could buy one intended for a "quiet" computer... if you don't need too much power, a quiet supply is possible. Maybe try the PC manufacturer "Shuttle"?
Oh! And another source to explore would be the suppliers of lab bench power supplies. Some are very feature rich, power capable... and expensive. I bet there are some inexpensive basic models, too, though.
