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COTS Voltage Ramp Module.
2

COTS Voltage Ramp Module.

COTS Voltage Ramp Module.

(OP)
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

RE: COTS Voltage Ramp Module.

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

RE: COTS Voltage Ramp Module.

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  
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RE: COTS Voltage Ramp Module.

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.  

RE: COTS Voltage Ramp Module.

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.

RE: COTS Voltage Ramp Module.

(OP)
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

RE: COTS Voltage Ramp Module.

(OP)
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

RE: COTS Voltage Ramp Module.

(OP)
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

RE: COTS Voltage Ramp Module.

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

RE: COTS Voltage Ramp Module.

(OP)
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

RE: COTS Voltage Ramp Module.

Why not just use a JFET and a capacitor?

Benta.

RE: COTS Voltage Ramp Module.

Show us, benta!

Gunnar Englund
www.gke.org
--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

RE: COTS Voltage Ramp Module.

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: Eng-Tips.com Forum Policies  

RE: COTS Voltage Ramp Module.

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

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RE: COTS Voltage Ramp Module.

(OP)
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

RE: COTS Voltage Ramp Module.

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

RE: COTS Voltage Ramp Module.

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.

RE: COTS Voltage Ramp Module.

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

RE: COTS Voltage Ramp Module.

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.
 

RE: COTS Voltage Ramp Module.

Gunner,

Based on what Keith originally asked, yes.  I have had the same problem when electronic engines came out and we needed to ramp up the desired speed instead of letting it just go right to rated. Since just about every application had the same requirement but different rates or the need for a permissive, a little logic controller was my best solution at the time.

I started originally using a Micrologix 1000 analog, I know BIG sledgehammer.  But if he wants to push a button, and have an output voltage from 0-5 or 0-10 VDC ramp up, you can write a few simple lines of code and make it happen.  If you want to get fancier, have an up and down input to fine tune.  Need to use on something with the same idea but a different ramp rate, make a change to the code.

If you need to turn it off faster than you can turn down a knob, you can wire an interface signal to reduce or turnoff the output based on a certain condition.

I carry a couple of the PICO relays in my truck, I run into lots of old stuff where sometimes you just need a quick solution to get something back going, these have done me well.  I know it seems like overkill, but to use a signal to ramp up a command to a large power supply, and maybe have a need to fine tune the level on the fly, plus maybe need to shut it off quick in case something goes bad, maybe a little smart relay can do what he needs.  Not sure but when he asked the question the situation sounded like ones I have run into, and needed a solution quick that was likely going to need to be tweaked as soon as the customer found you might really be able to fix his problem.

Besides, I like sledgehammers, only have to hit that nail once!

Mike L.

RE: COTS Voltage Ramp Module.

(OP)
I am back to considering the Micro PLC.  The customer is continually vacillating on requirements.  Dropping in a $150 microPLC provides the ability to change the ramp rate without a soldering iron.   It also allows me to automate some of the other functions.

They also want some data out on a new-from-scratch unit.  The microPLC can provide data out on some monitored values.  I can then see them coming back to this retrofit and asking for it to provide the data out also, which would be easy to do since the PLC would already be present.

I also wouldn't need to add a two rail PS because the PLC handles it.

Keith Cress
kcress - http://www.flaminsystems.com

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