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Simple circuit switcher needed - such a thing exist?

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phexagon

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Need a simple circuit switcher.

Something that passes through a signal from one of two pcbs. At a press of a momentary push button it passes through the signal from another pcb. The PCB are not related or connected to each other in any way.

Need the signal to be untouched - no voltage change or anything simply to pass through. Don't want to use optocouplers or anything like that, so does such a thing exist in the manner I have described. If a chip needs power to run on one it's pins that is not a problem as long as it does the job I need it to. I will accept a latching switch as the changeover switch if need be.

Here is a picture of what I mean:

**broken link removed**

It is desireable that it is a chip, it's form factor probably wouldn't be that shape I soppose. Any help would be appreciated.

Another example would be something like this but obviously not as cumbersome since I need it as small as possible:

**broken link removed**

I also don't want to resort to using an Arduino or anything like that. It needs to be cheap. I have no programmer knowledge but I'm gussing an off-the shelf chip can do such a thing. . . I need the circuit voltages to be untouched, in other words the thing just passes through the signal and doesn't interfere with it in any way.
 
What kind of signal levels are you wanting to switch, Voltage, Current, Frequency, AC or DC ?
 
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dc, small voltage (5 volts max - but unlikely to go anywhere near that imo), not sure about current.

As I just need it to act as a pass through I guess the only thing is if it doesn't go over a certain voltage and things like frequency wouldn't matter? I'm not an expert on these things :) thx for the reply.
 
Why don't you just use a simple DPDT (Double Pole Double Throw) switch? Based on your drawing and just switching a small voltage to choose A or B a switch would work.

Ron
 
sorry forgot to say this will be for many connections across each pcb so i'd rather not have loads of wires going to multiple switches from each pcb. I could sandwich the pcb's possibly using this method and maybe use some sort of harness like a ribbon cable to manage the connections. All depends on what my options are.

I am open to any suggestions requiring some programming requirements using a basic chip or something. No too sure which chip would be best or anything like that. The code doesn't sound too complex for what I need it to do so I guess I can get help with that if I have to go that route thx.
 
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OK, that makes a difference. I was seeing two boards and a few wires. :)

There are solutions and each has good and bad points. For example you can give this a read. I have made switching systems using CMOS chips like the 4066 quad bi-lateral switch but they have losses as can be seen in the data sheet. Depending on losses the signals need amplified to compensate.

Depending on the number of boards and lines and exactly what you are after there are relay boards that can be built using very small reed relay designs that are multiplexed to select given inputs to a single output pair. A Google of Relay Scanner Multiplex Boards or try Relay Scanner Boards should yield some off the shelf easily computer addressable solutions. The big merit to using a board like this would be just about zero signal loss.

This all comes down to the number of channels and exactly what you want to do. You can even do the layout and fabricate your own board or have one custom made.

Ron
 
thx i'll look into that.

I'm especially interested in the board if I need to do more than one of these.
 
4027 Dual JK Flip Flop with each Q and Q-not output switching one channel of a 4066 Quad Bilateral Switch. Two chips, two pair of analog (or digital) inputs, one pair of analog (or digital) outputs with 40MHz frequency response and 0.4% harmonic distortion. Sounds like an easy way to go for me. Some buffering might be in order to deal with a few hundred ohms of on resistance though.
 
4027 Dual JK Flip Flop with each Q and Q-not output switching one channel of a 4066 Quad Bilateral Switch. Two chips, two pair of analog (or digital) inputs, one pair of analog (or digital) outputs with 40MHz frequency response and 0.4% harmonic distortion. Sounds like an easy way to go for me. Some buffering might be in order to deal with a few hundred ohms of on resistance though.

I mentioned CMOS switching earlier, with a focus on the CD4066 quad bi-lateral switch. The problem when measuring voltages through one is the large losses. It just isn't in my opinion a good solution if you are scanning many inputs in data acquisition where accuracy is important. See the below image that simulates a CD4066 with a 5 volt input. My output is about 3.75 volts of the 5 going in.

That is why I believe most high speed data acquisition systems that scan multiple inputs mux using a relay card.

Just My Take
Ron
 

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I(R1)*10Meg=37.5KV?

It was an awfully long time ago and we never pushed them rail to rail, but we had no problems with distortion switching 200-500mVp-p, 1-4Hz signals with a 2.5V DC offset. There was a 1KHz application too but I was a noob at that point and never quite figured out how it worked. This was also back in the day of 8-bit sound cards.
 
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My bad on the sim. The load was 1K and not 10 Meg. That drops the voltage. I wish we knew exactly what the OP was measuring?

Ron
 
That makes the chip look better than its data sheet. 3.75V@1K implies an on resistance of 333Ω.

We found them sufficient for 8-bit data acquisition. (which we were doing through the old 15-pin game port connector :D) I've always been under the impression that you could get 10-bits worth of usable resolution, i.e. something like 9-bit accuracy with 11-bit linearity. Something a gifted audiophile would notice but not the average listener. Most of the testing we do here is considered good if we do better than 6-bits. :p
 
i've ordered 2 reed relays (just the individual components not a board or anything), will update later on in the week after some tinkering.
 
Keep us up on how it goes.

Ron
 
thx for the replies everyone. soz the reed relays are taking longer to arrive from the seller than anticipated but I will recap on what my thoughts are on them from what I can tell:

Relays allow one circuit to switch a second circuit which can be completely separate from the first. For example a low voltage battery circuit can use a relay to switch a 230V AC mains circuit. There is no electrical connection inside the relay between the two circuits, the link is magnetic and mechanical.

I mentioned CMOS switching earlier, with a focus on the CD4066 quad bi-lateral switch. The problem when measuring voltages through one is the large losses. It just isn't in my opinion a good solution if you are scanning many inputs in data acquisition where accuracy is important.

I can see what you mean about relays. Being that there is no voltage drop or anything affecting the signal form the pcb's it is ideal from what I can see.

The relay component basically allows one circuit to siwtch to completely seperate circuit. There is no electrical connection inside the relay between the two circuits I want to switch between since the link connecting them inside the relay is magnetic and mechanical.

I have looked at the Output Relay Scanners and came across one which was described as a row of relays on a panel that needed to be switched in order to turn on all the lights at the start of the day and off at the end of the day.

A relay scanner allows (amongst other things) a large group of relays to be switched at the same time. Since I only need this particular feature, I can save money designing a one-off item on stripboard using:

- stripboard
- row of reed relays
- row of screw terminals as the inputs from the pcb
- row of screw terminals as the outputs from the reed relays to the momentary push buttons
- common components (resistors and so on)

From what I can see a reed relay takes up alot of real estate on the stripboard, the ones coming are the same footprint as a 16-pin chip with a 0.1" pitch between the pins but their height is triple more or less. They only seem to come in single pole changeover or double pole changeover. Will update again later.
 
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