Bench Power Supply: Help

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ChibiM
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Bench Power Supply: Help

I am looking into getting a second hand Bench Power Supply, but I don't know anything about them. 

My use case: I want to test the LVP on flashlights. How deep can we go before a flashlight shuts off. 

But I have a few questions:

  1. Is my understanding correct, that you can't really charge a battery, because it won't 'slow down' when the maximum charge is achieved? 
  2. Besides checking the low voltage protection/cut off, what other things can this be handy for? 
  3. What specs are great to have? (I think most LEDs only go up to 12V, so for testing LEDs I wouldn't need a power supply that can do 60V, but rather more Amps?)
  4. Are there any other things I need to keep in mind when buying one?
  5. Would a 30V 5A be enough for 90% of what people use them for, regarding flashilght testing?
  6. What features could I be missing, when buying a 10-year old power supply, compared to a brand new model from RD Tech?

I'd like to buy a second hand one in the Netherlands, so before I jump on a 'good looking' deal, I'd like to know what else I should look at. 

Edited by: ChibiM on 04/01/2021 - 08:02
thefreeman
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  1. when the voltage reachs 4.2V (or whatever voltage limit you put or your CC-CV PSU) the current will progressively decrease, exactly like with a li-ion charger (=CC-CV) the difference is that the charger will stop when the current decreases past a certain point. Unless the PSU has a special charging feature it won’t, also some PSU might not like having a pre biased output (e.g a cell connected to it)
  1. hmm, lot’s of thing, but for flashlights specifically, you can make graphs like this for your reviews :

    Which shows more information than just LVP, you can infer from it what type of driver the light uses (fet, linear, buck, boost, buck-boost), you can test the springs resistance (voltage drop across it with know current), for example H600 have a shitty 50mΩ spring, which cause some non negligible efficiency losses, that could be an information to give in an extensive review.

Aside from that I don’t have much to say, I just have a dps5020 hooked to a laptop brick, RD PSU are cheap for the power.

ChibiM
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thefreeman wrote:
# when the voltage reachs 4.2V (or whatever voltage limit you put or your CC-CV PSU) the current will progressively decrease, exactly like with a li-ion charger (=CC-CV) the difference is that the charger will stop when the current decreases past a certain point. Unless the PSU has a special charging feature it won't, also some PSU might not like having a pre biased output (e.g a cell connected to it) # hmm, lot’s of thing, but for flashlights specifically, you can make graphs like this for your reviews : !{height:200px; width:200px}https://i.imgur.com/F9FQjZA.png!:https://i.imgur.com/F9FQjZA.png Which shows more information than just LVP, you can infer from it what type of driver the light uses (fet, linear, buck, boost, buck-boost), you can test the springs resistance (voltage drop across it with know current), for example H600 have a shitty 50mΩ spring, which cause some non negligible efficiency losses, that could be an information to give in an extensive review. Aside from that I don’t have much to say, I just have a dps5020 hooked to a laptop brick, RD PSU are cheap for the power.

Thanks for the explanation. Okay, that makes sense. A newer one, that has these fancy PC integrations could definitely have some benefits. But They are also much more expensive. 

I can have a normal 3A 20V for about $60, but a newer one would probably cost $150 or so, and I would only use it once in a while. 

CNCman
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PM Texas Ace, he will guide you. Wink
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There are two types of ps, Switching and linear. https://www.youtube.com/watch?v=PISZsjNhq7I
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I am trying to learn electronics so I can make some drivers and I know very little now. Maybe some experienced guys will give accurate advice for you. Here are some cheaper ps with decent reviews. I do wish I had purchased a programmable ps, in order to have the option of selecting output voltage and amps instead of letting the ps automatically giving the drawn amps.
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I wanted to test leds output to destruction and the one I purchased will not do that, but I did not know that then.
Take your time before buying !!
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https://www.amazon.com/Switching-Regulated-temperature-protection-Alliga...
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https://www.amazon.com/dp/B088YHYL3N/ref=syn_sd_onsite_desktop_175?psc=1...
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https://www.amazon.com/KAIWEETS-Adjustable-Switching-Regulated-Interface...
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https://www.amazon.com/Dr-meter-4-Digital-Multifunctional-Switching-Labo...
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I purchased this one. And upgraded the leads with 14ga silicon wire for more flexibility and less resistance.
https://www.ebay.com/itm/30V-10A-Adjustable-DC-Power-Supply-Precision-Va...
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But I wanted this one, Mastech Variable Linear Power Supply HY3010D.
http://www.mastechpowersupply.com/mastech-variable-linear-power-supply-3...
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jeff51
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I use one of these:
Amazon DROK Buck PS

You will need a power supply for the source. An old laptop power supply works well.
You can set a current limit and output voltage. Simple and cheap.
The meter can be set to show the output (or input) Volts and Current.
Won’t do any fancy charging functions, And you need a screwdriver to make CC or CV adjustments.
If you can find a used bench top PS, that would be nice. Unfortunately the older ones tend to be good but still expensive as they are usually marketed to professional use.
Used versions of the new inexpensive supplies for hobbyists don’t show up often – at least around here.
All the best,
Jeff

Sirstinky
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You can get a good power supply on AE for around $100. If you are mainly using it for lvp testing, then you don’t need it to go up to 20 A. 10A and 30v for 300 watts is sufficient. If you want to test leds, then you need higher amperage.

icpart
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RD6012 or RD6018 are very good power supplies for the money but they need external DC power suplly as input source.

ChibiM
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Thanks guys. I was thinking about the RD power supply's, but don't think I need that much Amps and features. 

I wish they had one below $100 including case and power supply. 

Yokiamy
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ChibiM wrote:

Thanks guys. I was thinking about the RD power supply’s, but don’t think I need that much Amps and features. 


I wish they had one below $100 including case and power supply. 

What kind of currents do you need?
And what voltages?