Need Help

[chuck conder]

Hi,

Not sure if this is the right forum to post this or not.


I am in search of someone that has the technical ability to help me out with a project.

I am looking to build a laser system with 3 mini green lasers wired in parallel to one driver...it get a bit more tricky but I can fill in the rest after we speak.

Please DM your info and hourly pay required or email me at chuckconder@gmail.com.

Thanks in advance,
Chuck

 

[Alaskan]

You need to wire them in series with a driver, it won't regulate the current to each diode unless you do it that way. Just ask some questions here if you want, or offline if you prefer, I guess you do or you wouldn't ask to take it offline. I just sent a message to you on FB.

 

[Laser Chick]

Hi chuck conder,

Good luck with your project.

 

[Sigurthr]

You'd either need to run three separate current sources on a single pcb, or run the diodes/DPSS modules in series. You can't just parallel up dynamic loads.

 

[Isaac Clarke]

if you run 3 diodes in parallel on a single driver the current will be divide between the 3 diodes....

 

[Sigurthr]

if you run 3 diodes in parallel on a single driver the current will be divide between the 3 diodes....

For ideal diodes that don't exist in the real world, yes. However every diode has a slightly different Vf, even down to the millivolt range, and this means whichever one with the lowest Vf will turn on first and conduct the full current and not share it with the other parallel devices. Additionally the thermal effects on forward voltage and impedance will not be balanced between the diodes so they won't share current evenly even if they did all start up simultaneously.

 

[Isaac Clarke]

thanks Sigthur now i learnt something new...

 

[Alaskan]

If trying to run the diodes in parallel across a single driver, the characteristics of the individual diodes can differ a little between each of them and that would cause unequal current flow, plus if one were hotter than the other, I'd expect that to cause an unbalance too, even if otherwise identical. I'd either run separate drivers, or if you can find a single driver which will handle the amount of voltage and current to drive three of them in series, which will be three times the voltage of a single diode, but same current, including the drivers drop out voltage loss too, I'd do that.

Edit: Sigurthr answered at the same time I was writing this. I was taking my time to get it right without having to edit it after posting, see how well that worked out

 

[Isaac Clarke]

thanks Alaskan, i learn something from you as well...

 

[Cyparagon]

...However every diode has a slightly different Vf...whichever one with the lowest Vf will turn on first and conduct the full current and not share it with the other parallel devices...

You can fix this by putting a small resistance in series with each diode. 1ohm or so would be plenty. It decreases the overall efficiency a bit, sure, but series operation and/or electrically isolating heat sinks is not always an option.

 

[Alaskan]

I wouldn't call that method best practice, but if it provides enough output, I guess why not.