Another adjustable constant current power supply thread

Hello,

I used to be into laser projects a lot back in the day with a handful of drivers lying around for just about any tinkering, however that is not the case anymore. However I do have a handful of diodes and modules lying around that I would love to play with again. I thought about building an arduino controlled power supply to drive them, however the task seems much more less common than I thought. I have not been able to find a clear answer while searching these forums or google, so I figured I would ask if anyone here has made one before and where should I start this project? It looks like a LM317 or LM350 is likely what I need to regulate the current. The LM317 looks like it only can handle up to 1.5A, so that may not be the best for some of the more powerful modules that I have, but the LM350 handles up to 3A which should be plenty. The most powerful module I have is a an M140 which specs at ~4v, 1.8A and emits 1.9 - 2.5W. Any guidance or suggestions would hugely appreciated.

Thanks!

The adjustable LM317 and fixed LM7812 type regulators are linear voltage regulators, not current regulators. You can adapt them to do both voltage and current by adding a low ohmic value shunt resistor which provides current sensing. The voltage developed across the shunt is fed into additional circuitry to provide adjustable or fixed maximum current outputs. Since these devices are linear regulators, they drop the voltage by way of a transistor in series between the input and output. The difference in voltage between Vin and Vout multiplied by the current being consumed by the load is the power that must be dissipated by the device. This is why linear regulators tend to have rather large heat sinks, they are quite inefficient compared to switch mode regulators. But, they offer much lower noise in the voltage delivered and are simple to design in comparison to switching regulators.

The Texas Instruments data sheet provides lots of application examples and explains the device in painstaking detail. Start with a review of how the device functions and then have a look at the application circuits for ways to achieve what you're looking to do.

http://www.ti.com/lit/ds/symlink/lm350-n.pdf

BTW, The LM350 is basically the same device as the 317 with a beefer pass transistor.

I feel like this would be a challenging task even for someone who is alright at electronic engineering :-/

EDIT I found a prebuilt digital supply online. It looks too good to be true. Does this thing look legit? I says it can save 10 profiles. This seems way too good to be only $26.

Link: http://www.dx.com/p/b3008-high-accuracy-dc-to-dc-constant-current-buck-module-green-272142#.U458-3KwJ3M

Much better price here:

http://www.ebay.com/itm/5A-Adjustable-Power-CC-CV-Step-down-Charge-Module-LED-Driver-With-Voltmeter-/221325518624?pt=LH_DefaultDomain_0&hash=item3388076720

Can they be trusted you think? I don't want to burn out ant of these diodes.

madz:
Can they be trusted you think? I don’t want to burn out ant of these diodes.

Well both are of Chinese origin. The best attitude to take with any power module is ‘trust but verify’. Test any power supply with ‘dummy loads’ (power resistors or automotive lamps) and measure voltage and current to see if values are stable and reliable after time. A good multimeter is of course a requirement before any DIY electronic project or experiment.

Good find. I am going to order one and try it out. I shall report back!

madz: Good find. I am going to order one and try it out. I shall report back!

Actually I would hold off. The title says CC/CV but I only see one adjustment pot so may be an error as the detail description says nothing about setting up constant current. However there are tons of such modules on E- bay so you should have a problem finding what you want at a much lower cost then that first one you posted.

This looks a little better: http://www.ebay.com/itm/New-Arrive-5A-LED-Panel-Voltmeter-Ammeter-CC-CV-Display-Step-Down-charge-Module-/131199702217?pt=LH_DefaultDomain_0&hash=item1e8c1c94c9

I literally, bought this after seeing this thread, i've bought loads of switching adj regulators and none of them have current limiting support..

So after reading this, i thought i'd take a punt at this ... http://www.ebay.com.au/itm/141241015464?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649

So it leads me to believe there's an SMD current regulator, now these pictures are kinda useless so I bought one to take a look at the current regulator IC chip, and then track down a supplier of that chip, because i have loads of cv switching regulators with few means (I have but it involves using a highish power resistor or a current sense resistor or just recently, measure the current and use a microprocessor)

long story short..

Why is there no good supply of high powered (such as the current regulator on the board i just ordered) dc dc current limiting ICs!

Take a look closely, you'll see an LM358! - is the opamp being used as a current limiter somehow?

cjdelphi:
Take a look closely, you’ll see an LM358! - is the opamp being used as a current limiter somehow?

Yes. http://www.mikrocontroller.net/attachment/149248/65_1301577300.gif

cjdelphi: I literally, bought this after seeing this thread, i've bought loads of switching adj regulators and none of them have current limiting support..

So after reading this, i thought i'd take a punt at this ... http://www.ebay.com.au/itm/141241015464?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649

So it leads me to believe there's an SMD current regulator, now these pictures are kinda useless so I bought one to take a look at the current regulator IC chip, and then track down a supplier of that chip, because i have loads of cv switching regulators with few means (I have but it involves using a highish power resistor or a current sense resistor or just recently, measure the current and use a microprocessor)

long story short..

Why is there no good supply of high powered (such as the current regulator on the board i just ordered) dc dc current limiting ICs!

Man I agree. I thought for certain there would be a shield for Arduino that could programmatically be controlled... :(

It would be more correct to say that the LM358 is part of the feedback path to limit current.

You keep saying diode, do you mean LED or Laser diode? I keep picturing you building all this just to drive a 1N4001... silly, isn't it?

I'm gonna delve into the world of cad and have a go at producing some open hardware circuits...

And one of my boards I'm going to create my own current limiting cc/cv circuit boards, ones where an attiny85 is the brain along with current sensing chips and a usb host.... I have plenty of projects in mind :)

I would be interesting to help. Mainly because I want to learn how this all works. So by help I mean learn.