What kind of component should I insert here to convert 0-5V to 0-100V

In summary, the conversation discusses building a stimulus isolator for biologists, specifically a voltage follower connected to a system that can be zapped with 0-100V. The individual has used a photovoltaic relay in the past, but now wants to control the voltage instead of gating it. They consider using op-amps, but are unsure how to connect the Earth for isolation. The conversation also mentions the use of optocouplers and a circuit suggestion from another individual. Ultimately, the conversation leads to the suggestion of using a fully isolated output DCP0105DS from TI to output 90V with amplitude adjustment at the output via a potentiometer.
  • #1
bill.connelly
21
0
Hi,

I'm trying to build what a biologist would call a "stimulus isolator". That is, I have a voltage follower connected to a system that I want to zap with 0-100V, so that the voltage follower doesn't see the voltage (much).

I have an A/D board that can put out 0 to 5 Volts. I want this converted to 0-100 V. The thing that vaguely complicates matter, is I that the resistance of the output (the input impedance of the system this is driving) will be variable.

I keep thinking op-amps, but then I get confused about how the Earth would be connected so that the output was isolated.

attachment.php?attachmentid=25743&stc=1&d=1273706690.gif


Previously I've used a photovoltaic relay (PVA1354) to do similar things, but now instead of gating the voltage, I want to control it.

Does anyone have any thoughts.

I apologize if this is monstrously retarded, I'm just a humble biologist.
 

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  • #2
Hi, I've had a few thoughts, how does this look?
attachment.php?attachmentid=25745&stc=1&d=1273712819.gif
 

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  • #3
You have the resistors the wrong way around. The bigger one should be across the opamp.

Normal opamps probably wouldn't handle 100 volts, but there are some audio amplifier chips that would go close. You would have to give them a split +50 volts--ground-- neg 50 volts supply.

And, sadly, optocouplers don't work like that. They need a small voltage to turn on and this produces light which makes a phototransistor turn on. This can then be used to switch an external voltage.
So, the input voltage is not passed on to the output.
 
  • #4
Yeah, I though this would blow your average OP-amp...
Double dang about the optocoupler... I thought it seemed to good to be true... thanks for your thoughts anyway.

Okay, say I was fixed the resistor lay out, and reduced the power voltage to 50V (making the resistors 1kOhm and 9kOhm). Is there anything that can simply isolate an input?
 
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  • #5
Okay, say I was fixed the resistor lay out, and reduced the power voltage to 50V (making the resistors 1kOhm and 9kOhm). Is there anything that can simply isolate an input?

Can't think of anything. It might be better to have an optocoupler being turned on by your 5 volt supply and then the output of this could turn on a transistor which controlled the 100 volt supply which you already have.

Doing this in a linear manner would pose a problem.

I hope you do not intend to harm small furry critters with this setup. I like furry critters.
 
  • #6
No, no... no furry creatures... cancer cells removed from a human decades ago...

This guy has posted something similar
http://www.nbb.cornell.edu/neurobio/land/PROJECTS/SIU/index.html
Except it seems very complicated. I can't figure it out enough to simplyfy it (I can't even figure out what the first transistor is for).

Also, he sais that Vcc = 6 volts, but he actually means 100V right?
 
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  • #7
The attached is a suggestion for a starter circuit.
 

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  • #8
bill.connelly said:
No, no... no furry creatures... cancer cells removed from a human decades ago...

This guy has posted something similar
http://www.nbb.cornell.edu/neurobio/land/PROJECTS/SIU/index.html
Except it seems very complicated. I can't figure it out enough to simplyfy it (I can't even figure out what the first transistor is for).

Also, he sais that Vcc = 6 volts, but he actually means 100V right?

No, I imagine that he means Vcc=5V (okay, he's probably powering this with 4 AAs, so maybe it is 6V). The output is 90V, however.

The first transistor is just to ensure that the input to the 4066 is around 6V or so (I believe):
http://www.fairchildsemi.com/ds/CD%2FCD4066BC.pdf

The beauty of the DCP0105DS is that it has a fully isolated output--the isolation is built in and the outputs are said to be floating. For that reason, the output from 3 of these (which are outputting 30V between the positive and negative rails) can be put in series to output 90V. TI seems to make this part now:
http://focus.ti.com/lit/ds/symlink/dcp0105.pdf

However, you'll note that the output amplitude adjustment happens at the output via the potentiometer.

EDIT: Reading through the description above the circuit diagram, I believe they state everything I just did above!
 
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  • #9
Thanks Skeptic
I've added in the isolators where I think you wanted them, is this correct?
attachment.php?attachmentid=25750&stc=1&d=1273738309.gif
 

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  • #10
Yes, thanks.
 

1. What is the purpose of converting 0-5V to 0-100V?

The purpose of converting 0-5V to 0-100V is to amplify or scale up a low voltage signal to a higher voltage range that is suitable for a particular application.

2. What type of component is needed to convert 0-5V to 0-100V?

A voltage amplifier or a voltage regulator can be used to convert 0-5V to 0-100V. Alternatively, a voltage divider circuit can also be used to achieve this conversion.

3. How do I determine the appropriate component to use for this conversion?

The appropriate component to use for this conversion depends on the specific requirements of the application, such as the desired output voltage range, input voltage range, and load impedance. It is important to carefully consider these factors when selecting a component.

4. Are there any safety concerns when using a component to convert voltages?

Yes, there are safety concerns when working with high voltages. It is important to follow proper safety precautions, such as wearing appropriate protective gear and using insulated tools, when handling components that convert voltages.

5. Can I use multiple components to achieve this voltage conversion?

Yes, it is possible to use multiple components, such as voltage amplifiers or regulators, in series or parallel to achieve the desired voltage conversion. However, it is important to ensure that the components are compatible and that the overall circuit is designed properly to avoid any potential issues.

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