COTS Voltage Ramp Module. 2

[itsmoked]

I'm looking for a gizmo that you close a contact or push a button on,(if panel mounted type), and the output voltage sweeps from 0V to 5V or maybe some other voltage (10V?) over a somehow settable time period.

I don't recall ever stumbling across something like this. Have you?

Keith Cress
kcress -

http://www.flaminsystems.com

 

[Skogsgurra]

The first hit when looking for 'ramp generator' is this:

http://www.rdlnet.com/product.php?page=170

Not exactly what you are looking for, but close. Time is fixed and cannot be changed. No capacitor to change.

Do you really need a COTS? A dual opamp and some resistors and a capacitor in a relay housing is what most people wold go for. Or one of the PIC Panic modules with some external circuitry to smooth the PWM ramp voltage.

Gunnar Englund

http://www.gke.org

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[jraef]

Kieth,
Look for the term Motorized Pot (no, that's not a Santa Cruz delivery van...) and/or its digital cousin, the Electronic Potentiometer.



"If I had eight hours to chop down a tree, I'd spend six sharpening my axe." -- Abraham Lincoln
For the best use of Eng-Tips, please click here -> faq731-376

 

[VEBill]

Is this for school?

(Sorry - I couldn't resist. [LOL] )

"How much current?" is an important question.

A power supply 'slave' input connection might allow a little tiny easy-to-make ramp signal to control many amps of DC.

 

[catserveng]

I've used both Micrologix analog PLC's (yeah I know a bit expensive) and PICO "smart relays" with analog output for ramping throttle signals on tub grinders and some other industrial applications, either 0-5VDC or 0-10VDC. Both worked well. Maybe not as cheap as you want, but ended being very flexible, I setup the PICO to be able to adjust the ramp rate from it's little screen.

Mike L.

 

[itsmoked]

Skogs: PIC Panic modules?

Ah man, that module would be the ticket but I need a time of about 3 minutes.

Jraef:

Ain't that the truth! Front page of today's paper was some local dork selling four flavors of pot ice cream.

VE1BLL; It's to ramp a 10kV power supply for a test fixture.

You know..

"We need this special discharge switch added and the supply increased from 4.5kV to 7.5kV."

"It will take 7 weeks because of the supply delivery?!!?!"

"&*&$^^#@#!!!"

"We simply must have in it two weeks, Oh, and add a ramping function."


Cat: It does seem like using a sledge hammer to hang a picture. But time is short so that's probably a pretty good deal. I'll check that out.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[itsmoked]

Skogs: PIC Panic modules?

Ah man, that module would be the ticket but I need a time of about 3 minutes.

Jraef:

Ain't that the truth! Front page of today's paper was some local dork selling four flavors of pot ice cream.

VE1BLL; It's to ramp a 10kV power supply for a test fixture.

They want the job done immediately if not sooner. Then after you hand them the quote they add "We also need a ramp function".

Cat; That sounds like using a sledge hammer to hang pictures but... I like it. I'll check that out.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[itsmoked]

Great.. After waiting 6 minutes and never having the post clear I repost what I was able to salvage only to NOW have the original appear.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[Skogsgurra]

Smoked

You can handle a soldering iron.

Get a dual opamp, a capacitor and some resistors and put it all together on a perf board as a temporary solution.

Make it work and let the temporary transform to permanent over a six months period.

Then, if they ever want a more commercial thing, you have probably found what you need.

Or I can send you an old 'Hochlaufintegrator' made by Siemens in the meantime. It will help me reclaim some badly needed shelf space.

Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[Skogsgurra]

Like this. Not much to it. You may want to refine it somewhat before operation OK.

Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[itsmoked]

That's what I'll do Gunnar. Thanks for the kick-off on it.

There's plenty of room in the fixture so I'll build it and get it working and then install it.

Thanks again.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[benta]

Why not just use a JFET and a capacitor?

Benta.

 

[Skogsgurra]

Show us, benta!

Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[jraef]

You had said COTS, but I should have known you'd rather roll your own.* Gunnar's drawing? It's the basic internals of a Digital MOP as I mentioned, although most also offered a Reset fuction that would either return to a preset you had set up or return to Zero immediately. A lot of VFD mfrs used to offer them as accessory boards, but now most of them have built that function in as standard so I don't see the boards available any longer.

*There I go with the pot references again...


"If I had eight hours to chop down a tree, I'd spend six sharpening my axe." -- Abraham Lincoln
For the best use of Eng-Tips, please click here -> faq731-376

 

[IRstuff]

Keith,

I don't that you've specified the accuracy or linearity of the ramp, but one obvious approach would be to use a precision voltage reference, ala

http://www.national.com/pf/LM/LM4132.html#Overview

which can be buffered and switched as needed to provide the input current for the integrator. Then, by using a higher quality series resistor and integration capacitor, pretty high performance and accuracy can be achieved.

Something similar is often used as the time reference for laser rangefinders.

TTFN

FAQ731-376

 

[itsmoked]

Thanks gents.
IR; This "added feature" is to replace the human who turned a knob for 3 minutes to reach the maximum. They are looking at the leakage current of the DUT. If it starts to have leakage they can stop it before an arc appears which destroys the $8k part. So the accuracy is not very important and the speed needs to be, "about 3 minutes".

Benta; That will work and be linear as apposed to exponential?

Keith Cress
kcress -

http://www.flaminsystems.com

 

[Skogsgurra]

Yes Keith. That is a smart and very simple solution. Use a FET (or bipolar) transistor connected as a current source. Run it from 15 or 24 V and the capacitor will charge linearly. The output voltage will be load sensitive and you may need a rather large capacitor for 3 minutes. Also, you need a zener to stop the charging from going to high - if too high a voltage is a problem.

I think it will work well if the only purpose is to replace a human hand.

Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[catserveng]

Yep, sledgehammer, that's me, too many years a mechanic.

I'm not good at putting components together and being a field service type of person, multifunction devices usually get me out of a jam in a hurry. I like the PICO solution only because they are fairly cheap compared to what the boss charges for my time, flexible so when I get an "oh by the way" I can in most cases tweak it to work still.

Sounds like you gotten lots of great ideas. good luck!
Mike L.

 

[Skogsgurra]

Mike - is that for this thread?

You mean that Smoked should use the analogue output of a PICO to ramp up the voltage?

Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[benta]

The JFET is one of the most "forgotten" active components in my opinion.

A JFET with the gate connected to source is an excellent current regulator.
The current range you can achieve is around 0.5...2 mA with the current JFETR offering on the market. It will work down to below 1 V, then it starts being resistive.

Vishay has them as ready-made current regulator diodes:

http://www.vishay.com/docs/70195/70195.pdf

Regards,

Benta.