Power Supply Recommendations

[RA_pierce]

Hi everyone.
I'm looking into purchasing a DC power supply.

Can anyone make any recommendations regarding what I should look for in a power supply?
What are some useful features?
How clean should the output be for laser diodes?
Anything else to think about?

I'd like to use it for testing laser diodes at a minimum and I am willing to consider more expensive options if there is a significant difference in quality or important features. Good value is definitely preferred.

 

[paul1598419]

I don't presently have a link, but you want a very clean and constant current and voltage supply with coarse and fine adjustments for both. You will probably want a 10 amp 30 volt supply as this will give you more options to test many diodes. If you get one used, it will be necessary to clean the pots and switches well as any noise can cause diode failure. It would be best if the leads zero out when turned on at 0 volts and 0 amps. Otherwise you will need to short them every time you turn it on before connecting to the diode. I use transistor sockets so it isn't necessary to solder on your diodes. You should be able to find one for ~$100.00 I would think. Better ones cost more. Sometimes much more.

 

[hakzaw1]

welcome back stranger..

this is a good time to get a great deal on a used PS.. reason? for me- I got a 3Amp that DTR was no longer using $40 shipped-- powers were going up and up. so if you are OK with less amps --I bet you would get some replies to a WTB thread.. I also jumped up to 5 amps and now that is not keeping up wit the 7 watters .. same with LPMs.. have you seen the one for $75?? PM me.. len
allow me to give your rep a bumpage.. +190 Welcome back

 

[paul1598419]

Here is a link to a 30 volt 10 amp adjustable power supply that ships from the US, new for $54.99. I have one and have gone through it with my scope and it is very clean, though some here have said they are too cheap. I have used it to test many laser diodes without any problems.

DC Power Supplies 30V 10A 110V Precision Variable Digital Adjust w/Clip Cable

 

[RA_pierce]

Thanks, guys.
I appreciate the input.
I think I want a new PS rather than a used one.

Hak - it's nice to be back.
Paul - I appreciate the link! Do you find that the transistor sockets are pretty reliable?

 

[Benm]

You probably don't need the 30 volts, so if you can find a 15 volt model with the same current at a lower price that would be preferable.

Also be careful with ones like the one linked in above.

There are tons of virtually identically looking ones on the market with numerous brand names, some real, some fake, some good and some bad.

If you have any option to get one from a place you can return it to free of charge, i'd go for that. You can measure things like power-up output spikes and prescence of large output caps (which are good thing for most applications, but not directly driving laser diodes!) quite easily with a dummy load and scope.

These properties are especially important when directly driving laser diodes, and could make an otherwise perfectly fine power supply useless for the purpose.

Consumer reviews will also be of little help there, those properties are no problem for the vast majority of users that just power up any electronics project. They will just look for the thing meeting max output specs and not overheating in the process, which some of them do.

 

[paul1598419]

Thanks, guys.
I appreciate the input.
I think I want a new PS rather than a used one.

Hak - it's nice to be back.
Paul - I appreciate the link! Do you find that the transistor sockets are pretty reliable?

I chose that particular link because it ships from inside the US. If you find you need to return it, you needn't send it to China. The sockets I use work very well for all the diodes I have tested. Some are high power diodes, others not so much. I never solder to a laser diode that I am testing any longer because I just don't need to. I have yet to lose one with the socket. I do solder leads onto the sockets though.

 

[Cyparagon]

I have one and have gone through it with my scope

What exactly have you measured? Is your scope capable of single shot capture? What about roll mode?

 

[paul1598419]

It does have a single shot, but not being a DSO, it doesn't have capture or roll mode. Roll mode, while being nice to have on a DSO is not necessary unless you want to do a running strip-like display of low frequency transitions from 5 ms or lower. I have been able to measure the immediate single shot of the PS at the time of turn on and also measure the noise level under load of changing voltages and currents. I have also measured these transitions while using a LD as a load to see any spikes or noise transitions while moving through the constant voltage and current levels without seeing anything out of the ordinary. Having done these things I can also report that I have yet to lose a diode while powering with my PS that is quite similar to the one I linked to.

 

[Cyparagon]

Roll mode... a running strip-like display of low frequency transitions from 5 ms or lower.

No, the frequency response of the roll mode depends on the scope's memory and time base. 5ms/200Hz response on a 0.5s/div timebase with a division count of 12 would mean a memory depth of 2400 points. That's just silly. Even a $200 scope has 1Mpts of memory.

 

[paul1598419]

Yeah, that was a typo. I meant 500 ms/ div or slower. Agilent, or what used to be HP will automatically kick out of roll mode at sweep rates higher than that. This is based on the DSO5000, DSO6000, and DSO7000 series scopes. But, I thought the purpose of your calling me out was that you thought this PS was not going to be up to the task of testing LDs. I still believe I have given enough information to show that it very well might be just fine. I know when I bought mine the specs were stated for the unit and before I used it I tested it to make sure.

 

[Cyparagon]

There's no need to get defensive. I was just asking for clarification, not "calling your out". The roll mode was a tangent.

 

[paul1598419]

No problem, Cyp. If I mistakenly took your question wrong I apologize.