The whole thing.
The "80 uA to 1.7A" can't be right. And why are two trimpots thermally coupled?
-- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
I had in mind using the regulator inside an opamp control loop, as a self-protecting power amp and heater. A small signal would be applied to the ADJ pin to set the current. Vout might go to ground through a small resistor to define the gain.
3t regs can be nice power amps.An LM317L with ADJ open makes a nice electronic fuse.
-- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
You say "resistors as heaters"? Probably someone has already mentioned this... why not use a power MOSFET as the heater straight across VCC and control current... then power is directly proportional to current. ...Jim Thompson
--
| James E.Thompson | mens |
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| E-mail Icon at http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
I think George couldn't stand the noise.
-- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
It was easier for me to simply link the whole thing. I was not suggesting using the whole thing. I linked only for the sqrt portion.
I too noticed that typo, but it is pretty obvious.
Den onsdag den 1. juli 2015 kl. 16.16.53 UTC+2 skrev George Herold:
I know Maxim, but ...
stick a MAX4210 in the heater control?
-Lasse
That's cool. Close a fast dumb subloop on heater power. That makes things power supply insensitive, too.
-- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
Oh the answer to that is easy, I don't know how to program an mcu. (Well OK an ardiuno with my son... if that counts.)
A $200 answer would be a labjack. Which is not a bad idea either, but I don't think my boss would buy it, and I don't want to spend the time trying to sell it.
George H.
Yeah, There's some concern about capacitive pickup. A low frequency and an LC on the output...
Oh, I could do pwm and filtering before the power stage. Hmm is that better or worse than four transistors? (I don't quite get the four transistor thing, so that would be more fun.)
George H.
The electronics mags are terrible about schematics. They just toss in some filler to space out the ads.
-- John Larkin Highland Technology, Inc picosecond timing laser drivers and controllers jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
Yeah, I've already proto-ed that. The powers that be, don't want it... though perhaps I should try to sell it one more time. One other huge advantage is that all the heat goes where you want it, no pass element with with cooling fan. (Which looks to be where it's heading.)
On the other side you can run resistors up to higher temperatures.
George H.
I don't know what a labjack is, but MCU programming can be very easy. I highly recommend learning Forth for nearly any MCU project. There are two commercial vendors that support a wide array of MCUs, MPE in England and Forth, Inc in the US. Both have great products and the way you would be using it, Forth is very easy to learn. There are open source versions that even live directly on the target such as Mecrisp. But they are typically not documented so well and are harder to figure out.
Programming MCUs gets harder when you have to program the peripherals such as the PWM which you won't be using. :)
-- Rick
I could pwm inside the circuit, (where no one would see me. :^)
Or an LC filter on the output.. that would help keep the pass element cool.
George H.
Are you talking about an H bridge? That is for driving with both polarities with a single power rail. Do you need that? PWM with a filter is a poor man's DAC. Why not just use the DACs in the MCU?
-- Rick
I've done some programming.. (Well ok sometimes too much playing around in my 20-30's) My boss is not interested, so unless I get a new job that's not an option. Which is mostly something I'm comfortable with. I enjoy analog, physicsy things more. I like to say that our company surf's on the trailing edge of technology.. keeping old analog ideas alive is part of it.
George H.
That makes the resistive load square-law again.
There is no free dessert.
-- John Larkin Highland Technology, Inc picosecond timing laser drivers and controllers jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
I have always ignored management opinions about technical issues. About almost all issues, in fact.
-- John Larkin Highland Technology, Inc picosecond timing laser drivers and controllers jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
I recall back after I had graduated college and got tired of being a chemist, maybe around 78 or 79'. I tried looking for an electronics job in my home town. Pickings were slim but I got an interview with a very small outfit in Point of Rocks... which is literally a stop on the railroad an not much more. This small outfit was just starting to look at digital and was prototyping some SSI type circuits using the dead bug method which I had never seen before. They were working on a sheet of plywood and had a simple circuit spread over a couple of square feet. Amazingly low tech even for that time.
Their main product was an amplifier they sold to the military for helicopter PAs which still used germanium transistors. Even I knew germanium has issues with thermal runaway. They told me what the advantage was for using germanium but I don't remember anymore. I believe they were gone in another five years or so. I guess after Vietnam was over the demand for their product dropped off a lot.
Weird that a company (back to yours) just refuses to consider the advantages of modern technology. By modern I am talking about stuff that has been in the mainstream for virtually all of my career. When I found a job it was working with 8080 CPUs.
-- Rick
I think the point is that if using a PWM from an MCU the appropriate adjustments are easy-peasy. So yes, this is pretty close to a free lunch.
-- Rick
sqrt(X) = antilog( log(X) / 2 )
Just divide the log by 2 and then do the antilog.
Preferably use a dual op-amp and preferably a dual transistor for log and antilog to maintain the same temperature.
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