exclusive continuous relay switching

Hi,


I would like to know if the following schematic is fine for a professional setup.




link: https://www.dropbox.com/s/9qfpk3x8rl7vlns/Screenshot%202016-08-22%2014.15.09.png?dl=0

The only downside for me is that with this circuit I need to implement an extra button to de-power all the relays. I would like that you could turn off the relay by pushing it again. I'm not to fond of the extra voltage rail but I can live with that.
I have been looking at illuminated push button switches in interlocking assemblies, but I can't find them at a sensible price. If anyone has any comments or tips, they're very welcome.

Best,

Zander

If you are not into micro-controllers of any sort then I guess it does the job. To me it looks typical of a pre micro logic solution which you would have found all over the place in reel to reel tape recorder from the 70s onwards so it is definitely professional in that sense .

You have a little 500Hz Schmidt trigger  oscillator as the clock. Initially all outputs are low and relays off. Pressing a button allows clock through to counter until that relay's output goes high when the clock stops and the relay is latched. Pressing any other button lets the counter run until its output goes high.

If you have a spare contact. making a relay latch itself is simple. An all off button would simply be a normally closed button in series with the supply. Very simple solution but downside are it uses a relay contact and buttons need to be able to handle relay current.

The 'modern' solution would be based around a low cost 14 pin micro-controller with an internal clock. Functinality would be easy to implement and modify/extend.

Cheers

Ian

ruffrecords said:

If you have a spare contact. making a relay latch itself is simple. An all off button would simply be a normally closed button in series with the supply. Very simple solution but downside are it uses a relay contact and buttons need to be able to handle relay current.

Click to expand...

IIRC, Zander asked for two functionalities: one of four selector and on-off function for each selected source without using extra pushbuttons. IMO, you can't do that in a simple way by using only relays.

The 'modern' solution would be based around a low cost 14 pin micro-controller with an internal clock. Functinality would be easy to implement and modify/extend.

Click to expand...

Does it mean that I can buy somewhere (here?) this already programmed to my needs micro-controller for max USD10 if that's so cheap and simple?

moamps said:

IIRC, Zander asked for two functionalities: one of four selector and on-off function for each selected source without using extra pushbuttons. IMO, you can't do that in a simple way by using only relays.

Click to expand...

I think you are right. I missed that point.

The 'modern' solution would be based around a low cost 14 pin micro-controller with an internal clock. Functinality would be easy to implement and modify/extend.

Click to expand...

Does it mean that I can buy somewhere (here?) this already programmed to my needs micro-controller for max USD10 if that's so cheap and simple?

Click to expand...

Definitely possible. It is not a difficult task to program such functionality into a small PIC microcontroller, for example, costing less than $3. I doubt what you want is already available but there are plenty of people here capable of designing it for you. How many do you need?

Cheers

Ian

ruffrecords said:

Definitely possible. It is not a difficult task to program such functionality into a small PIC microcontroller, for example, costing less than $3. I doubt what you want is already available but there are plenty of people here capable of designing it for you. How many do you need?

Click to expand...

I need two selectors one of four, each with on-off  (with memorized state when power is down), 4 pieces.

I'm not a 'micro' guy. But I do want to learn more as I would incorporate this on a PCB. Anybody know where to start? I don't know which search terms to use. Would I need to buy some sort of interface to flash/install the code on such microcontroller?


I'm a bit limited in time so I might be interested if some could pre-program such chip.


Zander

In the 'old days. all code was written in assembler which was unique to every micro. You had to understand the ins and outs of the peripherals of each device you used as well as a new instruction set before you could use it (not to mention the idiosyncrasies of the development kit unique to that devcie). Then, as micro memories got bigger, it began to become practical to write code in C but the compilers were terribly inefficient in their use of scarce resources. You also had to get an EPROM burner to load the code into the micro and a UV eraser to clean it out again before you could load the bug fixed next version.

Then along came Flash memory, the USB interface and half decent C compilers along with software tool for initialising hardware which meant you no longer had to have an intimate relationship with the hardware datasheets. Compilers run on a PC, send their code down via USB to a development board where you can both run and debug the code. Compilers are generally free and development boards are a few tens of dollars. All in all, micro development is a dream these days compared to when I started back in the mid 70s.

Despite these wonderful advantages, you still need to learn to write effective error free C and you still need to know basic software techniques like de-bouncing switches etc. This is not something to undertake if you are  'a bit limited on time'. Better to get someone experienced to do it for now but by all means learn later. There are lots of micros to choose from but my personal recommendation would be to go for the PIC series from Microchip. Thebasic C compiler and peripheral initialiser tools are free and run on Windows or Linux or Mac OS. The PICKIT 3 development device will program and debug almost any PIC and cost just £36 and you can get a pack of 3 prototyping boards with one  PIC16F1827  for £17.

Cheers

Ian

Zander said:

I'm not a 'micro' guy. But I do want to learn more as I would incorporate this on a PCB. Anybody know where to start? I don't know which search terms to use. Would I need to buy some sort of interface to flash/install the code on such microcontroller?

Click to expand...

Get an Arduino, a chip like L9823 (and an SOIC adapter board like the ones found on Ebay) and try to write a sketch that does what you want. If you get that far and want to make it professional, do it on a PIC. Or, if it is just a one-off and it doesn't have to be professional, stick the Arduino on there. Properly coded, an Arduino is perfectly reliable.