multiplex a 48V signal

[chico]

I would like to use a multiplexer on a group of analogue signals up to 48V. I have discovered that IC multiplexers don't work at particularly high voltages. Any idea of a good work around to this?

I wanted to use a multiplexing IC because I have 11 signals to toggle between and it seemed elegant, I suppose a rotary switch could suffice, but its not ideal since I actually have 2 groups of 11 signals to go through and i dont want 2 knobs ideally.
or
i could lower my signals and boost them back up, but then i would need that gain circuit on all 11 signals.

 

[ljcox]

I don't know of any high voltage MUX.

You could do the switching with MOSFETs.

You would need an IC deMUX that drives level shifting circuits (a bipolar transistor or a MOSFET such as the 2N7000) to drive MOSFETs.

 

[Reloadron]

You could consider designing a mux board using relays like these from COTO. Others make similar reed relays that would work. The link is just an example.

Ron

 

[canadaelk]

You did not mention current load, but check the PS7112/3 optical relay. They can be driven with a TTL based multiplexer and are not very expensive (relatively). E

 

[ljcox]

i could lower my signals and boost them back up, but then i would need that gain circuit on all 11 signals.

My puzzled.

Do you mean a MUX or a deMUX?

If you need 11 amplifiers, it implies that you mean it is a deMUX.

A diagram would help us to help you.

 

[ljcox]

You could consider designing a mux board using relays like these from COTO. Others make similar reed relays that would work. The link is just an example.

Ron

Yes, you could do aa 11 input MUX / deMUX with 5 relays.

 

[chico]

Sorry the current load is very little,
I have 11 voltage signals i would like to toggle between and display on my voltmeter so its an 11:1 switch really (11 inputs 1 output)

I have multiple groups of these that I would like to switch at once hence my desire to not use rotary switches.

what I meant when i spoke of lowering my voltage and boosting it was, i would lower all 11 voltage signals, say to x0.10 of the voltage, then put them through the switch, then boost the one output back up to its original levels 10x gain which i dont really want to do.

And im really confused about how those COTO relays work, I've never used a relay before, but I assume one of those pins enables it. :S

 

[RCinFLA]

**broken link removed**

 

[ljcox]

I looked at the datasheet of the HV2733 on the link posted by RCinFLA.

This would certainly do what you want, but it needs a serial data input.

However, I don't know what it would cost and also, it means that you would need something such as a microcontroller to generate the serial data to drive it.

Alternatively, you could do it using 5 relays as I said before, or you could do it using 11 LDRs illuminated by 11 LEDs.

I don't know if LDRs can withstand 48 volt, you would have to check that.

What determines which input you want to read?

For example, is it done by a counter?

I can post a simple relay circuit for you if you wish to take that path.

A relay has insulated wire wound around an iron core (an electromagnet), when you put a current through the coil, it attracts an armature which moves and causes a set of spring sets to move.

I suggest you do a Google search for "relays" as I expect there will be plenty of information available.

If you have any questions, just ask.

 

[Reloadron]

And im really confused about how those COTO relays work, I've never used a relay before, but I assume one of those pins enables it. :S

They are just small relays that work per the data sheet. You mention two groups of 11 channels so that would be 22 channels correct? So you want to choose 1 in 22 at the output correct? The question is do you want to switch the commons or do all channels share the same common?

The miniature relays can be strobed, scanned or selected however you wish to do so. This would be a basic relay type MUX (Multiplexer) card. A number of channels in with a single channel out. There are other types and this is but a single suggestion.

Ron

 

[Diver300]

What sort of voltmeter is it? Most voltmeters don't actually work on 48 V or so, but have some sort of potential divider in them.

You could put a potential divider in your 11 feeds, then use low voltage switching. Just read the lower voltage and adjust the voltmeter to suit.