1A LM317 driver with current selection switch

The Lightning Stalker · Aug 4, 2014

You'll know when it's getting too hot by a drop in output.
The LM317 are thermally regulated internally. They can
be paralleled. Give each one its own resistor.

IWIRE · Aug 4, 2014

Thanks for the info. I saw my output start decreasing when it was on the little piece of aluminum. It stays steady output on the heatsink or if I dial it down to 2.2a.

It's good to know they will work in parallel. I was wondering if each one would need a set resistor. Thanks.

I'm going to try it and see how that works for me. Do you know if they both can share a capacitor or does each one need it's own ? :beer:

alessnilsen · Aug 4, 2014

I think each 338 will need its own resistor, just make two drivers of 2,2A and then connect the two inputs and the two outputs together, the output cap can be the same.

Wait for somebody else to be sure.

---------

I was thinking in assembling my laser into a 15cm X 20cm wood board, and screw the power supply and the driver + laser module into it.

The control box will let me switch the laser on/of and control the power between 300mA or 1A.

IWIRE · Aug 5, 2014

alessnilsen said:
Wait for somebody else to be sure.

Me wait ? You must be teasing

I'll just keep trying till I make something work. Each mistake is a step closer to the solution

I can't use wood for mine. Wood is flammable. I'm using aluminum. Aluminum with vent holes for the battery compartment so it doesn't turn into shrapnel

Just kidding.
I'm going to use fuses to protect the battery pack . This thing will be pulling a minimum of about 15a and could be as high as 20a depending on my drive set-up I end up using. Fuses just seem like a good idea in this particular build. Especially since I'm the one building it. LOL !

Thanks for your help :thanks:

alessnilsen · Aug 5, 2014

You're welcome!

Me wait ? You must be teasing I'll just keep trying till I make something work. Each mistake is a step closer to the solution

That's the way! :beer:

I still doing tests and modifications on my driver, that's the flexibility that's a dummy load provides!

Fuses will work fine!

IWIRE · Aug 5, 2014

That's what I do when I'm not sure about a drive. A few months ago I was experimenting with sxb`s in parallel. I just hooked them up to a test load and monitored them

I have a heavy duty test load with a big heatsink and I'm getting ready to assemble a real heavy duty test load and incorporate a fan blowing across it just for stuff like this.

This is hard on test loads

alessnilsen · Aug 5, 2014

My test load just make me laugh from time to time, is 7 different diodes, all different sizes and some of different brands, each one have it's own specific voltage drop. All soldered together with a 1R resistor.

It get very hot at 1A, but since nothing burned, its OK.

I decided not allow the current to be changed when the laser is on. Because it can be very dangerous.
Since I will add a key switch to do this securely, it will protect the diode from any bad spikes that the driver can do.

IWIRE · Aug 5, 2014

Lol ! Try it hooked to a test load at 4a. The diodes will actually desolder themselves :crackup:

alessnilsen · Aug 5, 2014

Hahahah! :toilet: That must be true, see the poor thing: :crackup:

Today I done the control unit, with two switches (specially because it can go over and not inside the box as you can see), that's improvised from a old computer case, the part that covers the CD/DVD unit:

And waiting the module/heatsink + LD to arrive!

The Lightning Stalker · Aug 6, 2014

IWIRE said:
Lol ! Try it hooked to a test load at 4a. The diodes will actually desolder themselves :crackup:

If that starts happening, you need something like this.

IWIRE · Aug 6, 2014

The Lightning Stalker said:
If that starts happening, you need something like this.

That would do it ! That looks more like a rectifier bridge than a test load :crackup:

I have a test load board I got from another member here, I just placed another DigiKey order for the parts to assemble it. I think with good heat sinking and maybe a fan I'll be good. I ordered some resistors so I can set it at 2.2a also, or I can double up the resistors and get back to my 4.4a.

Right now I can't power the thing on long enough to get a good test and see if it will live. If I can run it for five or ten minutes without the magic smoke flying out of it. I'll say it will work and come up with a way to monitor the output.

Thanks for your help :beer:

alessnilsen · Aug 6, 2014

Hi The Lightning Stalker.

What kind of diodes are those? Never seen anything like this before.

IWIRE · Aug 6, 2014

alessnilsen said:
Hi The Lightning Stalker.

What kind of diodes are those? Never seen anything like this before.

It's a trip isn't it ! It really does remind me of a rectifier . Looks super duty for testing drives.

alessnilsen · Aug 7, 2014

That diodes don't seems easy to find, some can handle 100+A!

The Lightning Stalker · Aug 7, 2014

The ones in the picture are 1N1186 stud mount diodes,
and they are very old, date coded 1975! But they are
very good, JAN spec (Joint Army-Navy). Stud mount
diodes can be found in some older industrial equipment
like forklift battery chargers and welders.

If you have to buy new, it's cheaper to get the square
bridge rectifiers. If there is some old industrial
equipment lying around, though they can be had for
little or nothing.

alessnilsen · Aug 7, 2014

1975? Wow! Those things are old! For my searches, it support up to 35A.

1A LM317 driver with current selection switch

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