Author Topic: 5 ~ 10 watt variable current/voltage PSU for breadboarding?  (Read 9242 times)

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Offline nbritton

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5 ~ 10 watt variable current/voltage PSU for breadboarding?
« on: September 26, 2015, 01:00:25 am »
Ideally I'm looking for a digital display variable current & voltage PSU for use with breadboarding. It would be nice if it had pins that I can plug directly into the breadboard power rail and it also needs to be isolated from the mains so I can hookup my computer based analog discovery, arduinos, and raspberry pis. Extra features that would be cool are built-in USB power jacks and two outputs for +5V and +3.3V.
 

Offline Aodhan145

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Re: 5 ~ 10 watt variable current/voltage PSU for breadboarding?
« Reply #1 on: September 26, 2015, 01:06:20 am »
Why not a proper bench PSU?
 

Offline nbritton

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Re: 5 ~ 10 watt variable current/voltage PSU for breadboarding?
« Reply #2 on: September 26, 2015, 01:16:02 am »
Why not a proper bench PSU?

The cheapest digital bench PSU with more than 1 output is $150 on tequipment.net. If I went to the effort to get a bench PSU I would get the Rigol DP832. However, that thing is a monster relative to my needs at the moment.
 

Offline nbritton

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Re: 5 ~ 10 watt variable current/voltage PSU for breadboarding?
« Reply #3 on: September 26, 2015, 01:36:50 am »
I did find the MB102 breadboard power supply for $2, here: http://www.amazon.com/Breadboard-Power-Supply-Module-Solderless/dp/B00BXWV2F6

However, this leaves a lot to be desired. One issue it has is power can backfeed through the board (even if the switch is off) if your using multiple power sources, for instance the +5V USB coming from the computer. Also only rated for 700mA. Furthermore, it has no current limiting feature or display.

Looking for something in the $20 price range, in kit form or fully assembled.
 

Offline sarepairman2

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Re: 5 ~ 10 watt variable current/voltage PSU for breadboarding?
« Reply #4 on: September 26, 2015, 01:51:37 am »
ebay some old linear dual supply for 50$
 

Online T3sl4co1l

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Re: 5 ~ 10 watt variable current/voltage PSU for breadboarding?
« Reply #5 on: September 26, 2015, 01:55:25 am »
If you're really just starting out, I'd suggest any kind of supply for several fixed voltages (3.3, 5, 9, 12, 24, whatever), maybe an ATX supply with the output enable strapped on.  Then when you need an adjustable voltage, reduce it with resistors, or use an emitter follower or LM317 circuit, or any number of other approaches.  Later on, you can get a proper adjustable supply when you've outgrown your use of this method.

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Offline nbritton

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Re: 5 ~ 10 watt variable current/voltage PSU for breadboarding?
« Reply #6 on: September 26, 2015, 02:11:23 am »
If you're really just starting out, I'd suggest any kind of supply for several fixed voltages (3.3, 5, 9, 12, 24, whatever), maybe an ATX supply with the output enable strapped on.  Then when you need an adjustable voltage, reduce it with resistors, or use an emitter follower or LM317 circuit, or any number of other approaches.  Later on, you can get a proper adjustable supply when you've outgrown your use of this method.

Tim

I just recalled that I have an LM317 power supply sitting in storage, I would have to go hunting for it though. I have a crap ton of stuff in storage but I haven't had the time to go through it, just moved across the country.

I would like current limiting so I don't blow my circuits up.
 

Offline liquibyte

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Re: 5 ~ 10 watt variable current/voltage PSU for breadboarding?
« Reply #7 on: September 26, 2015, 02:20:01 am »
I like playing around with op amps so I came up with this.  You could probably bodge in an adjustable limiter but this one's set at a hard limit of 1A due to the transformer.  I've had it loaded down at 200mA and it produced less than 5mV ripple but I'm waiting on the boards to come in before I take it all the way to 1A.
 

Offline ez24

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Re: 5 ~ 10 watt variable current/voltage PSU for breadboarding?
« Reply #8 on: September 26, 2015, 02:31:57 am »
How about a laptop PS (like Toshiba) that is 19v 90watts and use Aliexpress bucks and 317s to make the voltages you want in step down steps.

As an alternative and if you have time to shop, a Power Designs power supply such as this one

http://www.ebay.com/itm/Power-Design-TW347D-Dual-Output-Power-Supply-0-16V-5A-0-18V-3A-/151825062210?hash=item23597a9942

There are several models, some which are very cool looking

They are very well built and this means you have a good chance of getting a good one on ebay.

An Aliexpress model buck:

http://www.aliexpress.com/item/Wholesale-Price-C-D-C-CC-CV-Buck-Converter-Step-down-Power-Module-7-32V-to/32339838120.html?spm=2114.01020208.3.72.w6361q&ws_ab_test=201556_2,201527_2_71_72_73_74_75,201409_2

these have current control and I have had good luck with them so far.  Notice this one has large heat sinks and coil.  This can handle 2 amps with no sweat.

One more thing that others have told me - the max current for a breadboard should be 2 amps

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Offline nbritton

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Re: 5 ~ 10 watt variable current/voltage PSU for breadboarding?
« Reply #9 on: September 26, 2015, 03:19:13 am »
One more thing that others have told me - the max current for a breadboard should be 2 amps

Per rail. Hence my frustration that the MB102 breadboard power supply is only rated for 700mA.

What about something like this?: http://www.amazon.com/gp/product/B00GZG7X9Y
« Last Edit: September 26, 2015, 04:48:21 am by nbritton »
 

Offline ez24

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Re: 5 ~ 10 watt variable current/voltage PSU for breadboarding?
« Reply #10 on: September 26, 2015, 04:59:24 am »
What about something like this?: http://www.amazon.com/gp/product/B00GZG7X9Y

Too bad about eBay.  From my experience buying power supplies has been my only successful test equipment purchases.

I would buy these (what you picked) and test it at 2 amps.  Absolutely do not believe  specs of 5 amps.  But it has the big inductor.

The 2 amp rating of breadboards came from several members, so I think this is a trust worthy number.

If you got three of these and a laptop PS supply you could come up with 3 different outputs all rated at 2 amps max and still be under the 90 watt rating of the brick.
And you have a voltage and current meter for each supply plus current limiting.  Remember you will need some power resistors to test and set these up based on Ohms law.

I may buy your selection and put together a 3 output power supply myself.

You would have dual displays for each voltage and current limiting, good selection.

Do you have a Harbor Freight IR meter?  If so you can test the heat ratings of the chips and heat sinks.

These things have high ripple, do you have a scope to test it with?  But from what I have found out, even though the ripple is relatively high, it is not a problem.  But I would place a 317 at the end of each to reduce the ripple a little just for fun. 



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Offline nbritton

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Re: 5 ~ 10 watt variable current/voltage PSU for breadboarding?
« Reply #11 on: September 26, 2015, 06:01:13 am »
If you got three of these and a laptop PS supply you could come up with 3 different outputs all rated at 2 amps max and still be under the 90 watt rating of the brick.

Yeah! I have an ancient 200W 19.5V power brick that I can cannibalize. The only issue is it has a grounded plug. How should I deal with that?
 

Offline ez24

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Re: 5 ~ 10 watt variable current/voltage PSU for breadboarding?
« Reply #12 on: September 26, 2015, 06:09:39 am »
If you got three of these and a laptop PS supply you could come up with 3 different outputs all rated at 2 amps max and still be under the 90 watt rating of the brick.

Yeah! I have an ancient 200W 19.5V power brick that I can cannibalize. The only issue is it has a grounded plug. How should I deal with that?

Take a pair of pliers and pull it out of the plug

Edit:  Since my house is old and has no ground, this is what I do.  If you have a ground then do as others have suggested and then ignore it.  You should have a neg wire that goes to the neg terminal on the buck and a positive that goes to the pos on the buck, as determined by a multimeter. (unless it is a Dell ps).  Then the neg will become the ground for your circuit.  This should be ok unless you start to deal with AC main voltage then all bets are off.

What I like about the laptop supply is all AC mains - remain on the floor and you will not have high voltage on your bench
« Last Edit: September 26, 2015, 06:41:09 pm by ez24 »
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Online bitseeker

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Re: 5 ~ 10 watt variable current/voltage PSU for breadboarding?
« Reply #13 on: September 26, 2015, 06:12:36 am »
If there are only two leads on the output, check if there's continuity between the ground prong and the negative side of the DC output. If there isn't, then the ground might only be there for the sake of the supply, not the device after it (i.e., laptop).
I TEA.
 

Offline CustomEngineerer

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Re: 5 ~ 10 watt variable current/voltage PSU for breadboarding?
« Reply #14 on: September 26, 2015, 06:44:14 am »
One more thing that others have told me - the max current for a breadboard should be 2 amps

Per rail. Hence my frustration that the MB102 breadboard power supply is only rated for 700mA.

What about something like this?: http://www.amazon.com/gp/product/B00GZG7X9Y

Thats not a PSU, just a Regulator. If you get that you will still need something to supply it with the 5V-30V DC that it needs. I also wouldn't trust that thing at 5 Amps, though you'd probably be ok with 2.
 

Offline nbritton

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Re: 5 ~ 10 watt variable current/voltage PSU for breadboarding?
« Reply #15 on: September 26, 2015, 08:18:58 pm »
If you had to choose between these two, which would you choose and why?:

http://www.amazon.com/gp/product/B00GZG7X9Y
http://www.amazon.com/gp/product/B013STFDTC
 

Offline ez24

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Re: 5 ~ 10 watt variable current/voltage PSU for breadboarding?
« Reply #16 on: September 26, 2015, 09:04:44 pm »
If you had to choose between these two, which would you choose and why?:

http://www.amazon.com/gp/product/B00GZG7X9Y
http://www.amazon.com/gp/product/B013STFDTC

Tuff when the price is so different

The one with the fan probably can do 3a.  The caps are low rated at 35v and I cannot see the coil.  If the coil is 101 then it is past my pay grade.

Why don't you buy both then report back to us on your review of them?  If you buy the $37 one it is not that much more to get the $17 one.

The $17 adjusts with a pot and from what I have been told they do not hold up to much usage.  So if  you are only going to buy one and plan to change the voltage or current often then get the $37 because if you keep making changes to the $17 it is likely to fail early.  So the $37 makes for a better adjustable supply.

So my suggestion is get both and use one as a fixed supply and the $37 for an adjustable supply.

Mounting is also an issue to think about.



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Online Rick Law

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Re: 5 ~ 10 watt variable current/voltage PSU for breadboarding?
« Reply #17 on: September 27, 2015, 01:12:25 am »
Why not get a digitally controlled B3603 at about the same price!  (Around $13 to $15 USD)



See the link below for a mini-review.  If this looks interesting, make sure you read the whole thread since a lot of info has been updated along the way as the thread grew.
https://www.eevblog.com/forum/reviews/b3603-dcdc-buck-converter-mini-review-and-how-the-set-key-could-be-fatal/


Rick
« Last Edit: September 27, 2015, 01:25:31 am by Rick Law »
 

Offline ez24

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Re: 5 ~ 10 watt variable current/voltage PSU for breadboarding?
« Reply #18 on: September 28, 2015, 03:00:06 am »
Why not get a digitally controlled B3603 at about the same price!  (Around $13 to $15 USD)



See the link below for a mini-review.  If this looks interesting, make sure you read the whole thread since a lot of info has been updated along the way as the thread grew.
https://www.eevblog.com/forum/reviews/b3603-dcdc-buck-converter-mini-review-and-how-the-set-key-could-be-fatal/

Rick
This has the ability to check the temps on the heat sink and be able to change the settings without turning a cheap pot.  I did not read the whole post because at the beginning there is a warning.  That stopped me cold, if there is a way to screw something up, I will find it.

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Offline TMM

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Re: 5 ~ 10 watt variable current/voltage PSU for breadboarding?
« Reply #19 on: September 28, 2015, 05:06:39 am »
maybe an ATX supply with the output enable strapped on
Wouldn't recommend it for a beginner as most modern ATX psus are more than happy to output 20A+ on their rails. Also unsuitable if you need low noise.

A low power unregulated DC wallwart/brick powersupply and an LM series regulator is what i'd recommend. Even without implementing a current control, you'll hit the internal current limit of the reg at 1-2A which is probably good enough to stop everything turning into BBQ.

« Last Edit: September 28, 2015, 05:10:23 am by TMM »
 

Offline ez24

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Re: 5 ~ 10 watt variable current/voltage PSU for breadboarding?
« Reply #20 on: September 28, 2015, 05:12:00 am »
maybe an ATX supply with the output enable strapped on
Wouldn't recommend it for a beginner as most modern ATX psus are more than happy to output 20A+ on their rails. Also unsuitable if you need low noise.

In my case I do not want the AC component to be on the desktop, thus the reason I want to start with a laptop brick and that will sit on the floor.  I know my scope is AC but I want the PS to be safe for children.
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Offline fivefish

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Re: 5 ~ 10 watt variable current/voltage PSU for breadboarding?
« Reply #21 on: September 28, 2015, 05:15:16 am »
Get an HP 6205C Dual Regulated Power Supply.  Less than $100 on eBay, find some deals for $49. 

 

Offline TMM

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Re: 5 ~ 10 watt variable current/voltage PSU for breadboarding?
« Reply #22 on: September 28, 2015, 05:32:55 am »
an ATX psu doesn't have mains AC exposed, all the output connectors are low voltage DC. The issue is that an ATX psu is a high current supply and will happily make small gauge wires red hot. Also all the output grounds of an ATX psu are referenced to mains earth so you can't gang up multiple PSUs to create split rails, or do anything that requires a floating ground. If you put a linear regulator like an LM317 on the 12V rail from the PSU you can get a variable output from a few volts up to about 9V and it will be safer than using the psus outputs directly as there is an internal current in the linear regulator so you can't draw more than about 2A. You may still kill your circuit under test but at least it's not going to make things red hot or start a fire.

Smaller brick supplies are usually double insulated instead of mains earth referenced, so you can float them (within reason...) e.g. create +/-9V rails, gang them up in series to get a higher voltage.
« Last Edit: September 28, 2015, 05:34:44 am by TMM »
 

Offline Flenser

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Re: 5 ~ 10 watt variable current/voltage PSU for breadboarding?
« Reply #23 on: September 28, 2015, 09:25:50 am »
If you had to choose between these two, which would you choose and why?:

http://www.amazon.com/gp/product/B00GZG7X9Y
http://www.amazon.com/gp/product/B013STFDTC

Julian Ilett has posted a video review warning about a bug that the first module suffers from where the current limiting does not work when the voltage and current limits are turned down to near their minimum:

 

Offline ez24

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Re: 5 ~ 10 watt variable current/voltage PSU for breadboarding?
« Reply #24 on: September 28, 2015, 06:53:13 pm »
I forgot about Julian's videos (isn't he a member?)
Notice the plug.

So I suggest to OP to go through them

https://www.youtube.com/user/julius256/playlists

Besides videos on the bucks he has videos on using the bucks in different projects

Thanks Flenser
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