convert 0-5v pluses to +/-15v pulses

[ericgibbs]

hi, softwareguy,

If you wish to maintain the +/-15V swing, squarewave over a range of frequencies, you will require an OPA that can operate from dual supplies of about +/-18V.

Can I ask what type of OPA's are you testing that require a +/-15V test input.???

 

[softwareguy]

hi, softwareguy,

Can I ask what type of OPA's are you testing that require a +/-15V test input.???

I don't have the schematic with me right now. All I am trying to do is simulate an input to a controller in which one of its inputs uses zero-crossing detection to make frequency measurements. The real input when the controller is installed in the real system is sinusoid up to 2.5kHz and a varying amplitude up to +/- 30V. So, a simple square +/- 15V (or +/-12V etc) will work fine for software development and bench testing purposes. I have a separate microcontroller that I can use to generate 0-5V pulse trains of whatever frequency I wish. I am trying to take that ucontroller output to drive a circuit that will make +/-15V and feed that input to the controller that has the zero-crossing detection input.

See the attached block diagram.

I may be wrong, but it seems that there ought to be a very simple way to create that circuit (I just don't have enough specific expertise/experience to design it). The biggest limitation I have is that I only have a single unipolar DC power supply to use for this circuit between the controllers. So, it seemed some sort of voltage divider opamp circuit and a DC-DC converter IC (like the sample I provided in other posts) might work.

 

[mneary]

You have all the pieces, now put them together.

The circuit you have on post #14 would work perfectly; just change the +15V on the comparator/op amp to +18V, and likewise change -15V to -18V. The reason for this is that these devices don't reach their rails perfectly and need a little overhead.

But this circuit violates the constraint of a single unipolar supply. So you need to somehow generate -18V from what you have. A "simple DC-DC converter" to the rescue. An example is the circuit which KMoffett offered in post #6.

Use the circuit in #6 to supply operating voltage o the circuit in #14.

 

[softwareguy]

Thanks, mneary!!

Is it possible to use a part such as

Digi-Key - 811-1594-5-ND (Manufacturer - NMV0515SC)

instead of building that circuit from discrete components (note that I don't have to reach a full +/-15, a +/- 11/12 will also work)?

Unfortunately, I don't understand the significance of an "NMA dc to dc converter" mentioned by ericgibbs (his quote below).

hi,
If its a NMA dc to dc converter, the answer is no.

 

[ericgibbs]

Thanks, mneary!!

Is it possible to use a part such as

Digi-Key - 811-1594-5-ND (Manufacturer - NMV0515SC)

instead of building that circuit from discrete components (note that I don't have to reach a full +/-15, a +/- 11/12 will also work)?

Unfortunately, I don't understand the significance of an "NMA dc to dc converter" mentioned by ericgibbs (his quote below).

hi,
The NMV is the same family as the NMA, its a dc to dc converter.

It expects 5Vdc in and give an isolated +/-15Vdc out.

It would be OK to power the OPA I mentioned earlier,

 

[qdn]

It would be OK to power the OPA I mentioned earlier,

What is an OPA?

 

[ericgibbs]

What is an OPA?

hi qdn,
Its an abbreviation for Operational Amplifier.

Some say Op Amp.

Ok.?

 

[qdn]

OK, Thanks!