Hello friends,

I'm looking for a solution how to switch between positions 1-3

I want to control with a digital switch controlled by plc?

Anyone have an idea?? more ideas?

thank you!

 

Welcome to AAC!
Why such low resistance values? With a total resistance of only 139Ω you risk stressing the MCU.
If you had much higher resistance values you could probably use simple, cheap transmission gates (e.g. CD4066) to do the switching.

 

Welcome to AAC!
Why such low resistance values? With a total resistance of only 139Ω you risk stressing the MCU.
If you had much higher resistance values you could probably use simple, cheap transmission gates (e.g. CD4066) to do the switching.

I'm trying to simulate PT100 sensor in 3 positions - -10c, 25c, 100c
CD4066 can't work with such resistors?

 

Hello,

Have a look at the MAX4991-4994 series.

Bertus

 

For these kinds of applications, I like to use reed relays controlled by the MCU.

 

For the outputs of the PLC, obviously you only need two, and probably contact closure outputs.
Is it a digital switch or PLC or are you substituting the name digital switch with PLC?
Max.

 

For the outputs of the PLC, obviously you only need two, and probably contact closure outputs.
Is it a digital switch or PLC or are you substituting the name digital switch with PLC?
Max.

I want to switch positions with digital IO of PLC,

I'm also open for other solution for example if you can advise a chip that in the input analog voltage (0-10) and the output will be impedance between 100 - 10K ohm.

 

I want to switch positions with digital IO of PLC,

.

So is this a problem? What PLC?
You only need two outputs.
Max.

 

I agree with Joey in that reed relays will give you low contact resistance in the 0.150 Ohm and 0.200 Ohm range. Their coil voltage at 5 VDC requires little current allowing them to be easily driven by a micro-controller. I used quite a few Hamlin reed switches and reed relays and they were always reliable. Coil currents of 10 mA are not unusual and switching times of 1.0 mS. Here is an example of just a few Hamlin reed relays, they make hundreds of types. A Google of Hamlin Reed Relays should get you plenty of hits.

The problem with a quad bi-lateral switch like the 4066 is they have a high resistance and you can't afford an unstable added resistance.

Ron

 

I would have thought the relay output of the PLC would be sufficient without adding any other device?
Max.

 

I would have thought the relay output of the PLC would be sufficient without adding any other device?
Max.

You can recommend how to wire such circuit?
I'm using UID-0016T, maybe it simple but I don't see the solution

Thank you

 

Looking at your specification sheet it looks like your version has 16 outputs Transistor, Source (pnp), 24VDC type. Your version does not appear to have relay outputs. I would use as I mentioned earlier, a reed relay having a 24 VDC coil. Your outputs switch a 24 VDC PNP output so one side of relay coil to your source and the other to ground. A Google of "Transistor, Source (pnp), Output circuits" will bring up dozens of examples of what you have. That would be my suggestion based on the data sheet you provided.

Ron

 

You can recommend how to wire such circuit?
I'm using UID-0016T, maybe it simple but I don't see the solution
Thank you

Yeah, that model uses transistor output, apart from snapping in a relay module in the rack, then the other solutions may be the way to go.
Max.

 

I decided that (see the picture) solution, but it seems to me very complicated...

 

it seems to me very complicated...

Nah. You'd need more components if you went the reed relay route, since each relay driver node would require a back-emf protection diode.

 

Have you read the data sheet:
Guaranteed On-Resistance

• 10Ω max (+5V Supply)
• 20Ω max (+3V Supply)

• Guaranteed 1Ω On-Resistance Match Between Channels (single +5V supply)

You have 24 volt switched PNP outputs. Your chip uses 5 volt logic. You are switching resistances to simulate a RTD 100 resistance. Your resistors are likely or should be 1% precision where a small fractional part of an ohm needs to be figured in and you plan to use the above switching? Those guaranteed maximum On Resistance will not even be stable. Wonder what will happen when you hit those switching inputs of your selected chip with the 24 VDC PNP outputs of your controller? Your solution will not work for reasons already covered. However, good luck with it. You do understand the importance of very low resistance switching in your application right?

The relays I suggested also include a diode suppression option (flyback diode) to suppress the back EMF.

Ron

 

Nah. You'd need more components if you went the reed relay route, since each relay driver node would require a back-emf protection diode.

While I always strive to keep component count to a minimum, I don't consider the count to be indicative of the complexity or adequacy of a design.

How many components should one use? Just enough.

 

While I always strive to keep component count to a minimum, I don't consider the count to be indicative of the complexity or adequacy of a design.

How many components should one use? Just enough.

The correct answer is Four. Worked with a guy for about ten years and Frank's answer was always four. No clue where Frank ended up but always remember "four" as the answer to everything.

Ron

 

Have you read the data sheet:
Guaranteed On-Resistance

• 10Ω max (+5V Supply)
• 20Ω max (+3V Supply)

• Guaranteed 1Ω On-Resistance Match Between Channels (single +5V supply)

You have 24 volt switched PNP outputs. Your chip uses 5 volt logic. You are switching resistances to simulate a RTD 100 resistance. Your resistors are likely or should be 1% precision where a small fractional part of an ohm needs to be figured in and you plan to use the above switching? Those guaranteed maximum On Resistance will not even be stable. Wonder what will happen when you hit those switching inputs of your selected chip with the 24 VDC PNP outputs of your controller? Your solution will not work for reasons already covered. However, good luck with it. You do understand the importance of very low resistance switching in your application right?

The relays I suggested also include a diode suppression option (flyback diode) to suppress the back EMF.

Ron

1. My plan is to work with Analog output of PLC, so 5 volt is not the problem.
2. I want to use potentiometers for calibrating the required resistance.

 

Then do it how you wish to do it. I merely made a few suggestions and covered why I suggested what I suggested.

Ron