Three Channel Selector with Flip-Flops

On a sunny day (Mon, 8 Sep 2008 14:42:59 -0700 (PDT)) it happened Fred wrote in :

Any binary counter will do, use the reset with an RC time to power up at zero count, for example the 74HC4040. Then use the first 2 output bits to drive lines A and B from a 74HC4051, a one of 8 analog multiplexer, or 74HC4052 (2x 1 of 4). Now you have 4 channels. To make sure you only count 0, 1, 2, stick Q1 Q2 (Q1 = Q2 = 1 = 3 dec) from the counter into a 2 input 'AND" gate, and have that drive the reset via for example a diode (so not to interfere with your RC reset at power up). Clock the counter via your switch, use some RC network as debounce.

Are you sure you don't want to use a PIC? How about a handful of

Cheers! Rich

After a quick look at the data sheets, it looks like the first chip is driven by only one switch for sequencial access of the three guitar channels. I need three switches capable of random access of the three channels.

It looks like a variation of the jeopardy circuit where each push of a button turns off the lamp previously lit and turns on its own lamp with out locking out another button push.

In this case it would be OK if at power all lamps remained dark until a button press.

Best...

Fred

On a sunny day (Mon, 8 Sep 2008 17:56:13 -0700 (PDT)) it happened Fred wrote in :

OK, seems I misunderstood your aplication. Apart from the PIC microporcessor already mentioned (doing it in software), you could use 3 flipflops, 3 switches, and connect Q of each flop via a diode to the reset line of the 2 others. So if Q of 1 goes high then 2 and 3 are reset, if Q of 2 goes high then 1 and 3 are reset, and if Q of 3 goes high then 1 and 2 are reset.

The power on RC reset via diodes to all reset inputs. Diodes are cheap. You can use a 74HC4051 analog selector, and 2 of the HC74 D flip flops. You need some resistors too.

Correction:

How about this:

| | | ------------- ------------- ------------- | Q !Q | | Q !Q | | Q !Q | | FF1 | | FF2 | | FF3 | | | | | | | 1 1/2 74HC74 set/ reset flip flop | !S !R | | !S !R | | !S !R | ------------- ------------- ------------- | | | | | | ---| |--- --| |--- ----| |--- | [ ] [ ] | | [ ] [ ] | | [ ] [ ] | resistors 10 k (this is the European symbol for resistor). | | | | | | | | | | | | | + + | | + + | | + + | | R1 | R2 | R3 | | | | R2 R3 | R1 R3 | R1 R2 | | | | | | | | | | --- --- | --- --- | --- --- | \\ / \\ / | \\ / \\ / | \\ / \\ / 1N4148 diodes or equivalent. | --- --- | --- --- | --- --- | | | | | | | | | ---------------- ------------ ----------- | | | | \\ S1 === \\ S2 \\ S3 selection switches momentary type. | | C1 | | /// /// 100nF /// /// How it works: C1 causes 'set' on power-up for FF1 to last a bit longer, so FF1 is on at power up.

Pressing S1 sets FF1, and resets FF2 and FF3 via the diodes. Pressing S2 sets FF2, and resets FF1 and FF3 via the diodes. Pressing S3 sets FF3, and resets FF1 and FF3 via the diodes.

Copyright Jan Panteltje 2008 - always. For reproduction in a magazine like for example 'electronics-weekly' contact me for where to send the millions.

set/ reset flip flop

k (this is the European symbol for resistor).

or equivalent.

switches momentary type.

power up.

You know, I got up this morning and started thinking just along these lines. I have yet to work with PICs, but have been meaning to get familiar with them. Do you think this solution would be easier or more simply implemented with one?

Thanks and best regards,

Fred

On a sunny day (Tue, 9 Sep 2008 08:35:08 -0700 (PDT)) it happened Fred wrote in :

Sure the hardware would be simpler, you can connect each switch to an input, and use the internal pull-up resistors.

With 3 switches, 3 outputs, ground and power, using the PIC's internal oscillator, you'd need an 8 pin PIC. Will set you back less then 3 dollars in single quantity, I use for example the PIC 12F629. The software is simple too, can be written in many ways... There is also the 8 pin 12F675 it has an ADC.

You would need a PIC programmer, the software is free. I think some are les then 50$. That investment will make sense if you are going to do more PIC projects.

Now that you got me headed in the right direction. I'm working out a circuit similar to what you provided, although with a Quad S-R Latch. You mentioned something about publication. And possible compensation??? :)

I see now that by using the PIC I could get rid of the resistors and diodes. Very neat. Would the PIC be able to source enough current to operate relays directly or would I still have to use a buffer?

Both those solutions are exactly what I needed.

Thanks,

FB

On a sunny day (Tue, 9 Sep 2008 15:40:56 -0700 (PDT)) it happened Fred wrote in :

If it is turned into an article for in a magazine, then you can ask money for it. This is very old technology, so I would not expect that to happen. For you it was free (as in beer) advice, do with it as you like. As to copyright, that always stays with the one who came up with it. In this case it would not surprise me if something exactly like this was published before.

On a sunny day (Wed, 10 Sep 2008 07:25:28 -0700 (PDT)) it happened Fred wrote in :

A PIC can sink a few milli amps. If you want to drive a relays, then either use a relays driver chip, or a resistor + transistor + diode, or a MOSFET + diode. A suitable MOSFET is the IRLZ34N, you can drive it directly from the PIC output, and it can sink 50A at 55 V, should be enough for a relays :-)

-------------------- + | | | --- [\\] / \\ | relays --- Si diode | | |----------- |--- ------||

all....

s.

If you get the right kind of PIC, and use the right pins, there will be programmable pullups included which will simplify the interfacee to the switches (but don't forget your (ESD) protection!).

ADC.www.microchip.comlistthemall....

I wonder if it would produce any noise that would be picked up by other parts of the amplifier.

Fred

Hey Jan,

That structure you presented is exactly what I need if using gates. I was wondering why you choose to use a chip with !S and !R inputs and pull them down. I >>> cautiously presume

On a sunny day (Fri, 12 Sep 2008 11:42:53 -0700 (PDT)) it happened Fred wrote in :

Hi, I chose the 74HC74 because I have used it some times. the rest is not edge triggered, but is a logic level passed on to the outputs, if you look up the data sheet, then you will see in the truth-table that if both set and reset are low, then both outputs Q and !Q are high. Clock and data can be connected to ground. There is in my view a slight advantage of having the switches connected to ground.

Very interesting. For what its worth you recieve the winning suggestion prize :)

The gate I found lacks data and clock inputs to worry about. It also has only one output. It comes in both nor and nand varieties. So, I could do exactly as you suggested. I found some very good optical devices to do the switching. So this should provide an excellent quick and quiet switch of the audio channels.

The only thing I trying to figure out now is how to initiate the switches in a sequential manner. That is when I switch channels, I want to mute the active channel with an RC slowed down turn off, then, un-mute the passive channel with an RC slowed down turn on.

This is something have to use a PIC to accomplish. I can look forward to that...

Thanks again,

Fred