"Industrial lego" voltage following/referenced power supply? - Page 1
Forum section: electronics / beginners

author: FlyingMoose
author_rank: Contributor
timestamp: October 13, 2023, 04:13:53 am
content: I'm working on a personal project that involves a peltier cooler (cooling only). Since peltier devices don't like PWM or on/off cycling, I want to drive it with a fairly steady DC voltage.I can easily buy a PID temperature controller that gives a 0-10V output (or 0/4-20ma). InkBird makes one, for example, that costs about $30.I'd like to find a DC power supply (maybe 10A) that will accept that 0-10V as an input signal and outputs the same voltage. Alternatively, a buck converter that will take in 12V from a power supply and output the selected voltage in the same manner. I can find power supplies that have a dial to adjust the voltage, but that is a potentiometer voltage divider that divides the output voltage down to an internal reference voltage.I have seen that I could use an arduino to do the PID controlling, output a PWM signal, select and use a MOSFET for switching and an inductor and diode to smooth the output.There are also voltage-to-PWM converters, but the only one I can find that outputs around 50kHz (to keep the inductor small) is a $2 chinese part that I'm not sure how much I'd trust. I'm not sure how well these would interact with a power supply. I can find better ones that output in the 1kHz range but the inductor would probably have to be huge (although I might be ok with that).I looked at the circuits for buck converters, and they also seem to set voltage by comparing divided output voltage with an internal reference, I can't seem to find one that lets you use an external control voltage.I could hack an existing power supply with a comparitor circuit, but I'd like to keep this robust as possible rather than building my own circuits (since I know enough to know that I don't know much). I'd really like to find a commercial solution that's already tested, safe, etc. I'm kind of surprised that such a solution doesn't already exist. Alternative ideas are welcome.

author: MrAl
author_rank: Super Contributor
timestamp: October 13, 2023, 06:03:29 am
content: Quote from: FlyingMoose on October 13, 2023, 04:13:53 amHi,To modify an existing power supply you really should have a schematic to be able to get it right.If not anything else, you could try a digital potentiometer, but you still have to know the voltage the original pot is working on and it has to match or be lower than the max voltage of the digital pot.

author: FlyingMoose
author_rank: Contributor
timestamp: October 13, 2023, 07:50:23 am
content: Maybe a simpler method than a digital pot is an LED run from the constant current 4-20ma signal, pointed at a photoresistor. Maybe they even make such a thing in an IC package (like an optoisolator but not logic-level).

author: Andreas
author_rank: Super Contributor
timestamp: October 13, 2023, 05:44:38 pm
content: Hello,There are Lab power supplies with a "remote control" input (usually 0-5V or 0-10V)But these are not the cheapest.https://www.conrad.de/de/p/voltcraft-hps-13015-labornetzgeraet-einstellbar-1-30-v-dc-0-15-a-450-w-remote-anzahl-ausgaenge-1-x-512321.htmlI would use a Korad KD3005 and do remote control via RS232.But I fear that this will not solve your problem with the temperature controller.(Except when your DUT and temperature sensor is directly in contact with the cold surface of the peltier)with best regardsAndreas

author: MrAl
author_rank: Super Contributor
timestamp: October 14, 2023, 02:26:49 am
content: Quote from: FlyingMoose on October 13, 2023, 07:50:23 amHi,They do, but they are not as repeatable as we would want for a power supply, but maybe in a closed control loop.There has been applications that use FET's as controlled variable resistors also.

author: FlyingMoose
author_rank: Contributor
timestamp: October 14, 2023, 02:48:43 am
content: For the power supply controlled by RS232, if I’m gonna use an arduino or something similar anyway, I’d just use the PWM output to control a MOSFET and then use an inductor/freewheeling diode to smooth the output (and might as well use it as the PID temperature controller too). It’s looking like this may be the easiest route.For the photoresistor option not being linear/repeatable, I was hoping that the “automatic/learning” mode on a commercial temperature controller would be able to figure that out, but maybe they’re not really up to dealing with a nonlinear response.

author: Terry Bites
author_rank: Super Contributor
timestamp: October 14, 2023, 09:12:22 am
content: Measuring your command voltage or loop current is easily done with your micro.TEC coolers like to be driven from a constant current source- a PWM current source is fine (rather than a PWM voltage source).How about an LED constant current boost or buck source with CV input? Most of them support CV and or PWM current control.In a closed loop control scenario you dont need super linearity in the controller's V/I characteristic.Measure the TEC+Load+tempsensor response first. It will have a very slow step response, no?When you stop yawning, you may decide that a critically to overdamped loop will suffice.Choose your P and I terms, D will probably be a bit superfluous and that will make it much easier to tune up.I'd slug it till it stops hunting and then chill a beer on it.Every man and his dog has a cheap LED driver ic for sale these days.The data sheets usually have simple application examples.External MOSFET types allow you to go as mad as you like with current.eg HV9910C, PWM or CV control from your dwino.

author: EPAIII
author_rank: Super Contributor
timestamp: October 15, 2023, 08:50:56 am
content: I am confused by your question. First you talk about needing a 0 - 10 VDC input which the output would follow in Voltage but with a (much?) larger current capability. But then you start talking about an Arduino and seem to think that the only way to control a power supply from that is to convert the output of the Arduino to a true analog Voltage. That is not the case and not necessarily the best way to do this.But the very definition of a "Programmable Laboratory Supply", it is a DC power supply where the output Voltage (and current) can be controlled by a DIGITAL input. So your Arduino simply sends the necessary numbers/commands over a digital link (USB or whatever) to the power supply and the supply outputs the requested Voltage, with an optional current limit. You are going to need a DC power supply anyway, so why not simply buy one that is programmable and use a digital connection?I am also confused by the current needed. You talk about mAs and then 10A. If a DC Voltage is really the way you must go, what current do you really need? I suspect it is in the Amps range, but then what's the mAs all about?By the way, you seem confused about how DC power supplies work. They do not divide their Voltage with a potentiometer to get an output Voltage. They SAMPLE the output Voltage and compare it with an internal reference (yes, using resistors and/or potentiometers) to develop a control signal that is used to control that output Voltage. But the output Voltage/current does not flow through those resistors and/or potentiometers.

author: FlyingMoose
author_rank: Contributor
timestamp: October 15, 2023, 12:26:42 pm
content: Quote from: EPAIII on October 15, 2023, 08:50:56 amThank you for your reply.I am aware that power supplies use a resistor divider to produce a feedback signal, not use it directly for output.The idea of using a lab supply occurred to me, but this is for a temperature-controlled box that I want to run long-term, I don’t want to have the size, expense, or complexity of embedding an entire lab power supply into it. Also, that would require another controller to read the output of the PID controller and write it to the power supply, and at that point I might as well just do all the control with an arduino. As a computer guy, I don’t trust software. I am aware that the PID temperature controller itself uses a microcontroller but these are very well designed and tested compared to an arduino etc. which is more of a prototyping thing.4-20ma is a common signal type in industrial sensors and controls (sometimes powered by the sensor or control and sometimes a dedicated 24V power supply on the circuit loop). 4-20ma is used because if it drops to 0ma the control will know that there’s a fault. Other common signal types are 0-5V, 1-5V and 0-10V. Most PID temperature controllers have a setting for which of these types of output to use.I mainly started this topic to see if anyone is aware of a commercial product to do what I’m looking for, that is, to take an input in the form of one of the common types of industrial control signals (4-20ma, 0-5V, 0-10V) and output a current or voltage based on that.The closest I’ve found are dimmable LED power supplies, which take a 0-10V control input and output a constant current or voltage based on that. I suspect, however, that they output PWM which will greatly reduce the cooling efficiency of a Peltier device.

author: FlyingMoose
author_rank: Contributor
timestamp: October 16, 2023, 04:01:23 am
content: So it turns out that HVAC/industrial 0-10V isn’t the same as lighting 0-10V, so I can’t use the lighting controllers.

author: FlyingMoose
author_rank: Contributor
timestamp: October 18, 2023, 08:02:16 am
content: Just an update in case anyone else is looking for something similar; the Mean Well DRA and SPV line of power supplies do exactly what I’m looking for.