+5v and -5v power from an Arduino

Hi there!

I'm building an analog switching circuit which is controlled by an arduino.

My circuit requires 25 4066 quad-analog switches. To get the required analog voltage range for the switched inputs, I need to provide +5v and -5v input power to all 25 of the 4066's.

I have tried to use a 1044 charge pump to get -5v, but it can't power more than one 4066, it seems.

I also need to be able to provide switch control voltage of +5v and -5v to the 4066s to turn on and off the switches. I am not sure that the Arduion pin's LOW output will be low enough to completely switch OFF the 4066 in the negative part of the analog signal.

Could anyone help me by providing an idea for a circuit that do all that, or maybe suggest a way forward?

Thanks so much,
Bob

You can buy a DC-DC module. Those small black boxes come with all kind of output voltages. The can have regulated or unregulated output.

If I had to make -5V myself, I would use an Arduino pin with a frequency and two transistors to drive a "voltage multiplier" or "charge pump" (diodes and capacitors) for -10V and regulate that (with 7905 or with feedback to Arduino).

Something like this: http://www.mbedded.ninja/electronics/components/capacitors#charge-pumps-bootstrapping

Can you tell about the signals that you want to switch ? Are they analog ?
When an analog signal is going through a few 4066, there is some loss. Even a single 4066 switch can not be used when the signal is a DC voltage that is measured.
There are also muxes that are very versitale in use. Perhaps they can be used instead of so many switches. Gammon Forum : Electronics : Microprocessors : 74HC4051 multiplexer / demultiplexer

Hi, it looks like you need to find a small 12V to 5V SMPS that has it input isolated from its output.
Use one for your +5V with Neg to Gnd and the other connected +5V to Gnd and -5V as your other supply.
The main requirement is that the input circuit is isolated form the output to allow the -5V config to happen.

Tom… :slight_smile:

You may find even 5V to 5V supplies, with isolation just for this job, then you only need one to make the negative supply.

dualsupply.jpg

I am not sure that the Arduion pin's LOW output will be low enough to completely switch OFF the 4066 in the negative part of the analog signal.

This chip is not well suited to bipolar signals, you will have to generate a virtual ground for the audio signal and the control signals will have to be boosted up. With a 10V supply (+ & - 5V) a logic high is typically 5.5V but can be as high as 7.5V. A logic low would be typically 4.5V but could be down to 3V. So the normal signals from the Arduino are not going to cut it. These values are taken from the CD4066 data sheet.
The 74HC4316 is a much better chip for you.

Do not remove the power from the multiplexer chip when there are inputs going into it as that will cause latch up and could destroy your multiplexer chip.

You will also get cross talk between the channels of the multiplexer.

If you're at the breadboard stage, an easy way to get -5V is to use a separate USB power adapter. You would connect it's +5V to the Arduino's GND and the adapter's GND becomes -5V. Use a PTC resettable fuse (i.e. RXE050 for 500mA) or similar for overload protection of the -5V wire.

I think the point is that he does not actually need a -5V supply, he needs a +10V supply.

I think the point is that he does not actually need a -5V supply, he needs a +10V supply.

If the OP needs +10V, the separate USB power adapter could be connected with it's GND to the Arduino's +5V. Now the adapter's +5V becomes +10V. A PTC resettable fuse (i.e. RXE050 for 500mA) or similar could be used for overload protection of the +10V wire.

Do you need +- 5 V at the output of the analog switch? If +- 2.5 V will work, why not capacitively couple your analog signal to the analog switch and use two equal value resistors, one to +5 and one to ground, on the input of the switch to give the signal a +2.5 V DC offset?
Now you can turn the switch off with a low from Arduino and you don't need -5 V power.

This forum won't allow me to modify the previous post, so I will add here that my suggestion does depend upon the input impedance of whatever the output is connected to. If it is quite low, the DC offset resistors will also have to be even lower. Could be a problem with signal level loss. I really need to know the impedances involved.

Thanks for all your answers!

I need to be able to switch an analog ac signal that may reach 10v peak-to-peak but probably less than 5v

I do plan on moving to 4316 switches to be able to use 0, 5v control logic, I believe.

I have come across a solution using an LM2596 to generate -5v but I haven't been able to make it work yet. According to the datasheet, this is possible.

I cannot use mains supply, except for testing, since this is a portable application.

More to come!
Ciao,
Bob

gratefulfrog:
I need to be able to switch an analog ac signal that may reach 10v peak-to-peak but probably less than 5v

Always better if you explain in full what that signal really is.

pegwatcher:
This forum won't allow me to modify the previous post

Now it will! :grinning:

The LM2596 output should be floating so if you connect the pos (+) output pin to your circuit ground the output of the LM2596 should be negative with respect to your circuit ground. Doing the same thing with any "floating" dc to dc converter (like a 5V wall wart) should work the same way.
Mike's comments were a reference to CMOS logic levels which are different from TTL (0-5V) logic levels.
If you are even asking these questions it is unlikely you have any experience with CMOS and may not understand his reply.