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Thread: Power supply question

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    Default Power supply question

    O.k. so, since I'm still a novice with all this and only have a mild knowledge of electronics... now that I'm aquiring diodes, housings, laserbugs, optics and other various and sundry bits... I guess I need to think about a power supply for setting things up and testing them. I know it's important to be able to adjust both voltage and mA. Any suggestions from people on a brand or model that's relatively inexpensive to get started with?

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    You don't necessarily need to be able to adjust the PSU, so long as it can provide enough voltage and current for your application.

    If you're using Flexmods, then they can cope with a wide range of input voltages - you just need to heatsink them adequately if using higher voltages.

    I'm a fan of using 12V supplies for flexmods as its enough volts for 445 diodes to run higher powers (5v is not quite enough for >600mW which is why you hear about people 'tweaking' them up a bit to 5.7v etc)
    Also, with 12V it means you have a power supply that can also run your 12V case fans too.

    Not sure how many diodes you'll be using or what wavelength, but if 445 and a up to a couple of diodes, try a 12V 5A as a starter - they're nice and cheap too.
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    Quote Originally Posted by Bradfo69 View Post
    O.k. so, since I'm still a novice with all this and only have a mild knowledge of electronics... now that I'm aquiring diodes, housings, laserbugs, optics and other various and sundry bits... I guess I need to think about a power supply for setting things up and testing them. I know it's important to be able to adjust both voltage and mA. Any suggestions from people on a brand or model that's relatively inexpensive to get started with?
    Sounds like you want to hook your diodes directly up to a lab supply...

    This is not really the recommended method of driving laser diodes, but it's a quick and dirty way to test things (I do it like this).

    I use a 20 years old 0-30V 0-3A supply.

    Voltage doesn't matter, the key is a good current limiter.

    Use a linear supply - I wouldn't trust a cheap switchmode supply to keep your diodes safe.

    If you are a novice with electronics I won't recommend doing this - one little mistake and your diode goes *poof*

    A LM317 circuit would be a lot safer imho.

    /Thomas

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    exactly what he said!!!

    you need two things to drive a diode safely. one is a regular power supply and the other is a current limiting diode driver (like the die4drive or the flexmod)

    i, too, am a fan of good old lab style power supplies (big caps etc). i don't really like switching power supplies much

    instead of the lm317 (my favourite little ic) i would recommend the LT1083CP. exactly the same thing, but it can handle up to 7.5 amps


    i am also thinking of building a variable bench power supply with it
    "its called character briggs..."

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    Hummm..... maybe I need to re-figure how this works somehow. More I think about it, the more it makes sense though. Maybe I'm looking at needing two different things. I DID state I'm still a bit behind on electronics and only have some of the basics.

    Example one... Buffo and I have been discussing building a red module, similar to a Maxiz and I have aquired most of the parts thus far. In looking at and reading about various diodes, they make reference to certain specs such as 4.8v @ 550mA gives you X number of milliwatts of power and, at 5v @ 600 mA gives you x number of milliwatts of power. But, don't exceed 650mA because you'll blow this or that diode. Well... I picture someone with a power supply where your turning dials and reading a VU meter to establish the number of volts and milliwatts you're applying. I thought that WAS a function of a power supply and, I guess on a benchtop...it is. I think that's what I was initially asking about.

    Yesterday I received some Flexmods in the mail and I guess in a projector or...with this red project... you just apply the voltage (preferrably a "regulated" supply between 5 and 24 volts) and the adjustment of mA becomes a function of the flexmod. (?)

    Anyway, that leads me to my next thought which is, again...what power supply to purchase. What am I looking for to buy and stick in a projector or, to this red build, that supplies 5 volts or 12 volts? Regulated versus unregulated... I understand an AC to DC converter like a wall wart is unregulated. Am I looking at a computer power supply since there are usuallyleads that supply 5 volts, others 12 etc. Or, is there some other type/brand of supply I should be looking for? (Like Traco for example which Edison uses in his projectors.) I'm just not certain what I should be buying to supply power to things like my 200mW LaserWave 473 or, this red once I start to built it or, a green when I go to buy one to match it.

    Still slightly confused...

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    Nope, you've pretty much got it.

    You want a regulated supply at the required voltage. The flexmod is then used to set the current reaching the diodes, usually variable by the modulation lines, but capped at whatever you set it up for e.g. 650mA

    I use separate supplies for groups of diodes, so if my 12V PSU dies the green at least still keeps working (5v). Redundancy is something might want to consider as part of your build.
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    You are using Bonetti's defense against me, ah?

    I thought it fitting, considering the rocky terrain.

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    Thanks Norty... I'm liking the looks of something like this for experimentation on a bench with diodes:

    http://cgi.ebay.com/TEKPOWER-LINEAR-...item2eb3c6ebbe

    or this:

    http://cgi.ebay.com/Jetstream-JTPST3...item2eb39a08ba

    the only thing I'm still not quite clear on however, is what I need to be actually looking for with respect to going in a projector. WOULD a computer PS such as a decent Antec or something like that actually be adequate?

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    Quote Originally Posted by Bradfo69 View Post
    WOULD a computer PS such as a decent Antec or something like that actually be adequate?
    On paper: "Yes".
    In practice: "Thoroughly not recommended" (When the 3rd one on my RGB packed in, months down the line, I finally binned them off and put in proper caged SMPS's)
    - There is no such word as "can't" -
    - 60% of the time it works every time -

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    I got this one for bench work. Hope it's o.k.

    http://cgi.ebay.com/TEKPOWER-LINEAR-...item2eb3c6ebbe

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    Quote Originally Posted by Bradfo69 View Post
    I got this one for bench work. Hope it's o.k.

    http://cgi.ebay.com/TEKPOWER-LINEAR-...item2eb3c6ebbe
    Looks fine

    If you are going to power diodes without a driver do the following:

    1. Power on the supply without the diode connected.
    2. Set the voltage a little above the diodes Vf (I use 5V for red diodes)
    3. Short circuit the output, and adjust the current to your desired level.
    4. Power off the supply (keep it short circuited)
    5. Connect diode
    6. Power back up and enjoy

    /Thomas

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