Recommendations for a 20A or higher bench PSU, for under $150 shipped?

[rhd]

Hi if you want to regulate voltage up to 36 volt and current up to 3 amp then BangGood sell a great little digital current voltage regulater for £8.23 around $12.75 i have a couple and they work great i use my old computer power supply (500W) and you can set both the current and voltage down to point 1 volts and amps.
this is the link to them :-http://www.banggood.com/DC-LED-Digital-Controlled-Step-Down-Driver-Power-Module-p-910096.html

as long as you want less than 3 amps i doubt you could get better for the price, I use them to test diodes just with two wires with croc clips on if you even short out the cables you will not draw more current than you have set it to.
hope this helps, regards Poppy Ann.

That does not help, nor does it address the OP or the most recent post.

 

[crazyspaz]

Yikes...thats unfortunate. Who the hell would design something like that??!?

 

[Alaskan]

The way I understand it the problem is the voltage is too high as well as the current before you can do CC mode.

Only three things you can do that I see:

1. Sell or return it and get something else

2. Buy an external module to use with it for CC control

2. Insert voltage dropping diodes and only use it for higher current CC needs.

You could get a lower voltage output from the power supply through the use of voltage dropping power diodes. I sometimes do that instead of using a full blown voltage regulator when I only need a few volts lower but at 20 amps, they would need to be some big ones on heat sinks.

Maybe some diodes like this mounted on a couple of heat sinks, or insulated from one another in series somehow on a single heat sink: http://www.ebay.com/itm/2-X-VISHAY-...ERY-CHARGERS-POWER-SUPPLIES-NEW-/371021668224

You would never exceed their current rating with that power supply.

Edit: Here's the data sheet http://pdf.datasheetcatalog.com/datasheet/good-ark/70HFR160M.pdf

From close to zero current to 20 amps the voltage drop is .7 to just under 1 volt each at 25C (infers a heat sink to keep them that cool). I'd buy at least four of them and put them all in series to get your 3 volt output knocked down to start close to zero volts, if that is your need.

I don't know how well this kind of setup will work due to the .5 volt knee for each diode, whether your CC circuit in the power supply will be as smooth as you would like, but I expect it won't cause any bumps when adjusting current, once you get past the minimum forward bias point for all of them in series.

 

[crazyspaz]

So the problem is the voltage is too high as well as the current before you can do CC mode, the way I understand it. You could put some diodes in series to reduce the output voltage, as an offset, as long as you knew the exact drop of the diodes, to keep the voltage lower to a device, but I don't know how to deal with the current minimum at 1.5 amps.

Only two things you can do that I see, sell it and get something else, or buy an external module to use with it for CC control and use power diodes to reduce the voltage to your device.

Could, but that kinda defeats the purpose of an adjustable power supply :/

 

[Alaskan]

Yes, it is only a work around. I edited the post since you last quoted.

 

[djQUAN]

Really? You want me to start pumping potentially substantial current / voltage through shorted leads? This is nonsense.

Yes, I do that to my bench supply all the time. Just short the output terminals (use a thick enough wire) then adjust output current. Voltage will drop to nearly zero to limit current to set value. Well, that's how mine works.

edit:
BTW, if you plan to power LEDs or laser diodes. Once you set the current as per above, reduce the voltage again to zero (don't touch the current knob as it is set to your desired value) and connect your load. slowly increase the output voltage until the diode conducts and the PSU goes to CC mode.

Setting the voltage above the Vf of the diode is asking for trouble as there is a largish output capacitor and the CC feedback on these supplies are pretty slow so it will take some time until it goes from CV to CC mode. Raising the voltage slowly allows it to go to CC mode gradually preventing current spikes to the diode.

 

[Alaskan]

I've done that too, if the CC circuit is in there, shorting the leads to set the maximum current will work but I normally don't like to do that with a power supply capable of higher currents. It might be just fine to do so if you set the current low or even to near zero to begin with, but I am concerned it is hard on them if you don't do that first.

 

[Sigurthr]

Honestly at this point I'd return it if I could, if I were in your shoes. If I couldn't return it I'd build a dual LM317 + PassBanks CC CV supply and just use the housing, pots/knobs, meters, and stepdown transformer out of that chinese piece of junk. I've never heard of a piece of lab equipment, cheap or not, having such a ludicrous procedure.

 

[Alaskan]

Or, ship it to me with some of your MODOCS and I will send you a 115 VAC input 0-7.5 volt DC output CC power supply good for 100+ amps, but you have to trust me to ship it

 

[rhd]

Or, ship it to me with some of your MODOCS and I will send you a 115 VAC input 0-7.5 volt DC output CC power supply good for 100+ amps, but you have to trust me to ship it

While I appreciate the offer, you might send me a power supply that runs on energized 7th dimension hypermagnetic ora fields, and unfortunately my power outlets are only wired up to supply 110.

I'll pass

 

[Alaskan]

My bad, 100-120 VAC and 47 to 63 Hz.

I'm wondering if this is because you can't trust me after I said I sent those 20W 808nm diodes and they never showed, but you never gave anything in exchange for them so that's why I'm offering the trade that way, even though it was the post offices fault for loosing them and my stupidity for not insuring them with tracking. I probably ought to put it back up on ebay where I originally bought it without a guarantee it was good (which it is) and sell it anyway, I need the money more than I need another power supply and I have two of these. That's my Russian wife holding the power supply, I don't have a lab set up at home.

 

[rhd]

I'm wondering if this is because you can't trust me after I said I sent those 20W 808nm diodes and they never showed, but you never gave anything in exchange for them so that's why I'm offering the trade that way, even though it was the post offices fault for loosing them and my stupidity for not insuring them with tracking. I probably ought to put it back up on ebay where I originally bought it without a guarantee it was good (which it is) and sell it anyway, I need the money more than I need another power supply and I have two of these. That's my Russian wife holding the power supply, I don't have a lab set up at home.

Lol, no. It was just a reference to your silly "wooo wooo" science posts

That's a cool PSU, and I wouldn't be opposed to buying it from you, but I've never had success trading anything.

 

[Alaskan]

Oh, well, I did get out of hand on that thread, my apologies, I have been a dick a time or two on that subject but it is one I am very fascinated by, just chalk me off as a crazy if you want, but I do have a good heart and have always been considered honest.

I can put it up on ebay if you want, safe for both of us that way, I suppose paypal is also a good way to go without ebay taking a cut. Shipping won't be cheap from Anchorage, Alaska 99515 to you, about 25 pounds packed I imagine, maybe a few pounds less. The DC output is on the back, a pair of bus bars to bolt your wires to.

 

[rhd]

Oh, well, I did get out of hand on that thread, my apologies, I have been a dick a time or two on that subject. I can put it up on ebay if you want, safe for both of us that way, I suppose paypal is also a good way to go without ebay taking a cut. Shipping won't be cheap from Anchorage, Alaska 99515 to you, about 25 pounds packed I imagine, maybe a few pounds less. The DC output is on the back, a pair of bus bars to bolt your wires to.

Well, what's the price you're looking for, and what do you expect shipping to cost (I'm actually pretty close to you).

If you need a BC postal code to calculate to, try V5A1A1

 

[Alaskan]

Ouch, expensive even though close, I just drove through there in July moving to Alaska, by the way, so it's been there already. Would you be willing to pay 150 plus 75 shipping with 2 Modocs thrown in? That's a deal, I could easily get 250+ on ebay if guaranteed good, I would guess. They go for 400-600 from time to time. I will guarantee it good, I've been using it too.

 

[rhd]

Ouch, expensive even though close, I just drove through there in July moving to Alaska, by the way, so it's been there already. Would you be willing to pay 150 plus 75 shipping with 2 Modocs thrown in? That's a deal, I could easily get 250+ on ebay if guaranteed good, I would guess. They go for 400-600 from time to time. I will guarantee it good, I've been using it too.

That's probably a fair offer and all, but it adds up to about $300 bucks, and that's several times higher than I have in my budget for a third PSU that is meant to replace a second PSU that was meant to replace my first.