Please help! :)

[Rachel]

Hi all,

My problem is I ran 4 diodes in parallel with a flat-ish battery (did not have much juice left in it) and only 3 turned on.
I've checked the circuit and it seems sound. Could it be possible that the battery did not have enough charge to power the 4th? I know lasers demand current till they blow themselves, hence why 3 only tuned on, this is why I think it might be the low battery.

I haven't checked the connections to the anode and cathode yet, but I think that's fine. The polarity is correct just to answer your question in advance. Could it be that the battery is just low on juice, or the lm317 bust or resistor? I don't think the lm317 or resister is bust, just hoping You have any suggestions !

Thanks
Rach

 

[diachi]

Did you have balancing resistors on the diodes? Could be something to do with that, although I'd expect them all to still turn on. Perhaps the 4th diode is dead?

 

[Rachel]

I just have standard resistors with my lm317. Like I said it might be the connectors to the laser, just wasn't sure if this would be a problem with the battery running low.

The circuit is fine, Visually, everything goes to where it should, maybe Its static ? Can't see why it's not showing unless the connector is not in properly, I'll test the continuity later. Or the battery not being able to turn the last one on coz the other 3 are taking all the supply. They're 4W lasers, and we're really dim lastnight, this is why I need to recharge my battery.

Hope this helps give anymore answers

 

[bdgreenb]

What battery are you using? If they are running properly in parallel they all should be running about the same. It's possible 3 were just over the threshold with the last being just under. Charge your bats and get back to us

 

[WizardG]

What do you mean by `in parallel'? Does each diode have its own LM317 or they all hooked together to the same regulator?

4 watt lasers? Each ONE of those would pull more current than an LM317 can provide.

From your post it sounds like you have four 4-watt laser diodes connected in parallel to one LM317. Do not do that. It will not work.

 

[Rachel]

What battery are you using? If they are running properly in parallel they all should be running about the same. It's possible 3 were just over the threshold with the last being just under. Charge your bats and get back to us

thanks for ur comment db. I'm thinking along the same lines as you. It can be possible! Since the battery was so low

Yes I think it's very interesting of science to cut off the last one! Exciting. They 4W and they have burnt a hole in my leather purse. This time they haven't even burnt tissue. I left the battery for a few weeks since I last used it

And yea will do, it's something cool if that's the case anyway! Electricity is wonder stuff!

 

[Rachel]

What do you mean by `in parallel'? Does each diode have its own LM317 or they all hooked together to the same regulator?

4 watt lasers? Each ONE of those would pull more current than an LM317 can provide.

From your post it sounds like you have four 4-watt laser diodes connected in parallel to one LM317. Do not do that. It will not work.

Sorry I wasn't clear wizard,

Each laser has its own circuit (lm317) ran in parallel with each other.

 

[diachi]

What do you mean by `in parallel'? Does each diode have its own LM317 or they all hooked together to the same regulator?

4 watt lasers? Each ONE of those would pull more current than an LM317 can provide.

From your post it sounds like you have four 4-watt laser diodes connected in parallel to one LM317. Do not do that. It will not work.

Where are you getting the 4W Number from?

You are correct, that wouldn't work, I just don't see that number?

 

[WizardG]

Where are you getting the 4W Number from?

You are correct, that wouldn't work, I just don't see that number?

From Rachel's second post, "They're 4W lasers, and we're really dim lastnight"

From her reply I understand that each laser diode has its own LM317, which is good, but the LM317 regulator won't pass enough current for any 4 watt diode to reach full power, which is less good.

 

[diachi]

From Rachel's second post, "They're 4W lasers, and we're really dim lastnight"

From her reply I understand that each laser diode has its own LM317, which is good, but the LM317 regulator won't pass enough current for any 4 watt diode to reach full power, which is less good.

My bad, I missed that!

Yeah, an LM317 can't provide enough current to power a 4W diode... 1.5A max. An LM338 would manage it, they're basically just the 5A version of the 317 - circuit is the same.

 

[Rachel]

From Rachel's second post, "They're 4W lasers, and we're really dim lastnight"

From her reply I understand that each laser diode has its own LM317, which is good, but the LM317 regulator won't pass enough current for any 4 watt diode to reach full power, which is less good.

Wizard and Diachi,

I should've considered this, however I have 3 x lm317 in parallel with each other with a 1ohm resistor = 1.25... X 3 = 3.75 to answer that question! Then this is ran in parallel with the other 4 in the same way.

It's parallel parallel if that makes sense

 

[Cyparagon]

First rule of troubleshooting - check voltages. With battery negative as reverence ground and with the circuit ON: What is the battery voltage? What is the OUT pin voltage? What is the ADJ pin voltage?


Please draw a schematic of what you're doing (if only a crude one). Most of the work here so far is trying to figure out what you've built, and that isn't an efficient use of time when a drawing is a viable alternative.

 

[Rachel]

First rule of troubleshooting - check voltages. With battery negative as reverence ground and with the circuit ON: What is the battery voltage? What is the OUT pin voltage? What is the ADJ pin voltage?


Please draw a schematic of what you're doing (if only a crude one). Most of the work here so far is trying to figure out what you've built, and that isn't an efficient use of time when a drawing is a viable alternative.

That's good idea checking the out puts on the lm317 tbf, I'll check that out in the troubleshoot plan

I have 4 LD in parallel with each other.
They all run off their separate circuits with 3xlm317 also in parallel. - hope that helps

I think db might be right tho, maybe I'm just reading what I want to hear xD

 

[diachi]

Wizard and Diachi,

I should've considered this, however I have 3 x lm317 in parallel with each other with a 1ohm resistor = 1.25... X 3 = 3.75 to answer that question! Then this is ran in parallel with the other 4 in the same way.

It's parallel parallel if that makes sense

That still doesn't work - the total current required by 4 diodes in parallel will still be more than the LM317s can provide. Current is added in parallel while the voltage drop remains the same. So if you have 4x diodes needing 3A each (Just throwing that number out there as an example) you'd need to supply 12A, which 3x LM317s can't do, not even close.

You also need a balancing resistor on each diode in a parallel configuration... As for your LM317 setup, I'm not so sure about that...

To do this with LM317s you'd need to have the diodes in series, or have more regulators. You'd also need to increase the input voltage to the LM317s to account for the larger drop of 4x diodes in series.

A schematic showing what you're doing would be helpful, and maybe some pictures of the setup.

 

[Rachel]

That still doesn't work - the total current required by 4 diodes in parallel will still be more than the LM317s can provide. Current is added in parallel while the voltage drop remains the same. So if you have 4x diodes needing 3A each (Just throwing that number out there as an example) you'd need to supply 12A, which 3x LM317s can't do, not even close.

You also need a balancing resistor on each diode in a parallel configuration... As for your LM317 setup, I'm not so sure about that...

To do this with LM317s you'd need to have the diodes in series, or have more regulators. You'd also need to increase the input voltage to the LM317s to account for the larger drop of 4x diodes in series.

A schematic showing what you're doing would be helpful, and maybe some pictures of the setup.[/

I've had all 4 on before on my prototype model(breadboard) and running his with battery 7.4V capable of 248A. It burnt Through a lot of stuff The current demand for the diode is 3.5max and the voltage is 4.8V

 

[CynicalBrad]

I do believe Rachel is saying each of the four diodes is being ran from 3xlm317's for a total of TWELVE LM317's.

Essentially 4 separate laser/driver combos being ran from one input power source.

(+)           [battery]           (-)
 |                                 |
  >           3xLM317&LD          <
 |                                 |
  >           3xLM317&LD          <
 |                                 |
  >           3xLM317&LD          <
 |                                 |
  >           3xLM317&LD          <

Is that about right?
(Too lazy to make a proper diagram of what I believe is being done by the OP Rachel.)