Author Topic: Buck or boost?  (Read 1969 times)

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Offline paulca

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Re: Buck or boost?
« Reply #25 on: January 14, 2018, 04:12:42 am »
At least the ones on RS are likely to actually work properly.

Yes.  Hmm.  This seems to behave like a small linear regulator.  I might have to probe it and disconnect some pins to find out.

Also, how "cowboy" is this... I didn't have a spare heatsink handy.  Hunted round my bits and pieces boxes for something I could drill a hole in and use as a heatsink, when I found my power resistors.  So I bolted the power resistor to the LM2576 as a heatsink.  Works great.  Innovate.
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Offline bd139

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Re: Buck or boost?
« Reply #26 on: January 14, 2018, 04:33:15 am »
Nothing wrong with that! Bulldog clips and copper pipe caps make reasonable “quick” heatsinks as well. I’ve even built a circuit on a bean can lid because I ran out of FR4.
 

Offline paulca

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Re: Buck or boost?
« Reply #27 on: January 14, 2018, 04:47:52 am »
Nothing wrong with that! Bulldog clips and copper pipe caps make reasonable “quick” heatsinks as well. I’ve even built a circuit on a bean can lid because I ran out of FR4.

LOL.  I was considering using a beer can, but figured I might slice myself open cutting the thicker lid section out.

I ordered 5xLM2576's from RS.  If their inductors weren't a scandalous price I'd order a few of those too.
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Current Open Projects:  3 Channel Audio mixer with DAC, BT, pre-amps and h/phone amp, WS281x LED controller Version 2 5V/5A w/Atmega328, FY6600 Power supply, 5A DC Load (Still!)
 

Offline paulca

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Re: Buck or boost?
« Reply #28 on: January 23, 2018, 07:15:58 am »
At least the ones on RS are likely to actually work properly.

That's if RS could send the right components.  ;)  Got some random 3 pin SMD thing in a bag that said LM2576T-05 G on it.  Returned.  Just waiting on a second delivery of the same thing. 

Anyway.  I got two things in the post.

Car 12V cigarette lighter socket with QC3.0 port 2x normal ports and a volt meter.  The phone loves it, goes straight to 9V and pulls 1.5A.  "Turbo Charge Connected".  The voltmeter is handy as I'm running it off a lithium pack that is not protected.

and this little gizmo:
https://www.ebay.co.uk/itm/262407885292

Which, asides the worrying green caps, seems to be fairly decent.  I've only tested it to about 3A and it doesn't squeal, get warm or even sag voltage.  It's holding 5.15V dead steady.  The phone likes it, pulls 1.6A from it happily.  I seems to have 3 ICs, one is about 20 pins, though I can't think what for as it's not QC.  Also seems to have a shunt resistor, so maybe it's current limited.   It's pretty too.  From the ebay warning about devices not pulling 1A, they seem quite proud of it too.

EDIT: Actually this is reported as having 2xQC2.0 ports, which is why the phone is pulling high current.  I can assume it only supports 5V though.

I think I can tick the USB charging box as DONE now.

I'm still going to build the buck converter, just for fun.
« Last Edit: January 23, 2018, 07:29:34 am by paulca »
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Current Open Projects:  3 Channel Audio mixer with DAC, BT, pre-amps and h/phone amp, WS281x LED controller Version 2 5V/5A w/Atmega328, FY6600 Power supply, 5A DC Load (Still!)
 

Offline bd139

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Re: Buck or boost?
« Reply #29 on: January 23, 2018, 09:43:54 am »
That doesn't surprise me with RS. I regularly get sent the wrong bits. Sometimes they're worth a lot more than what I ordered though! Ordered a 59p pack of Vishay MRS25 resistors and got a reel of tantalum capacitors worth a small fortune. Didn't say a thing  :-DD

Looks good. Some of the little switchers from China are pretty good. I tried to blow a couple up and I couldn't.
 

Offline paulca

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Re: Buck or boost?
« Reply #30 on: January 27, 2018, 06:30:00 am »
One thing I just found about the chinese buck converter.  If it is has no load on it, it fizzes the power input badly.  I happen to be powering the buck converter and the headphone amp off the same battery and if I remove the load off the buck converter I hear horrible fizzing.  Not loud, but very noticeable.

I'll keep it loaded or depowered I think.
"What could possibly go wrong?"
Current Open Projects:  3 Channel Audio mixer with DAC, BT, pre-amps and h/phone amp, WS281x LED controller Version 2 5V/5A w/Atmega328, FY6600 Power supply, 5A DC Load (Still!)
 

Offline paulca

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Re: Buck or boost?
« Reply #31 on: January 28, 2018, 07:27:19 am »
Credit were credit is due.  RS helped me sort out the regulators.  I ended up having to ask them to do a stock check as they assumed I had ordered the part in error having sent back what looked like a correctly shipped part.

They phoned me on Friday and said they did indeed have incorrect stock and have refunded my purchase AND sent a replacement arriving on Monday.  I love free stuff.
"What could possibly go wrong?"
Current Open Projects:  3 Channel Audio mixer with DAC, BT, pre-amps and h/phone amp, WS281x LED controller Version 2 5V/5A w/Atmega328, FY6600 Power supply, 5A DC Load (Still!)
 

Offline paulca

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Re: Buck or boost?
« Reply #32 on: January 31, 2018, 09:20:50 am »
So I got the "proper" LM2576s.

I'm not sure they were the problem.  I got a worse voltage drop!  4.03V at 0.3A.

I replaced the inductor with a branded panasonic one that cost me £5!  I checked all my capacitors with a component tester.  Everything checked out.

So I did a bit of double, triple checking, googling and the only answer was "breadboard".

So I soldered it onto a perf board.  I cramed everything as close as possible and used schotky diode leads for most things.  Didn't have time to solder a USB socket onto the board so connected it to a USB breakout board with croc clip leads.

4.25V at 0.3A.  WTF?

I was raging.  So... I went to probe pin 2 of the regulator to see the waveform was still there and still 60Khz.  I missed and probed pin 4 (output).  Low and behold, what did I find?  4.96V.  Confirmed with my multi-meter.  At the end of the croc-clip leads... 4.24V

I expect these croc-clip leads are made out of soft Chinese cheese.  Most like about 2 strand aluminium.  They are only 0.5m long.  So they aren't much use.

I expect if I spend the time to solder a USB socket onto the perf board it will give me close to 5V and I can load test it.

That said, it was a learning experiment, I've learnt a few things.  I don't know if it's worth keeping around and wasting a USB socket on.  It's not like I will use it for anything.  I might keep the board in case I have a project which needs a 1-3A 5V switching supply daughter board.

I also expect the orginal LM2576s (and inductor) were fine and my breadboard was playing funny buggers with the switching of the regulator. 
« Last Edit: January 31, 2018, 09:22:36 am by paulca »
"What could possibly go wrong?"
Current Open Projects:  3 Channel Audio mixer with DAC, BT, pre-amps and h/phone amp, WS281x LED controller Version 2 5V/5A w/Atmega328, FY6600 Power supply, 5A DC Load (Still!)
 

Offline james_s

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Re: Buck or boost?
« Reply #33 on: January 31, 2018, 02:58:52 pm »
I'm surprised the regulator worked at all on a breadboard, switching regulators are fussy about layout, especially grounding and the feedback loop.

I had a similar experience with cheap clip leads. Eventually I bought some high current silicone insulated wire from a hobby supplier, it's the stuff used to carry power to the motors in RC models. I got some quality alligator clips and made up a bunch of jumpers, never had any problems with them.
 

Offline paulca

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Re: Buck or boost?
« Reply #34 on: January 31, 2018, 06:56:12 pm »
I had a similar experience with cheap clip leads. Eventually I bought some high current silicone insulated wire from a hobby supplier, it's the stuff used to carry power to the motors in RC models. I got some quality alligator clips and made up a bunch of jumpers, never had any problems with them.

My plan, kinda.  The silicon RC wire is expensive though.  It's like 1.99 a meter for 18AWG.  From hobbyking it's about half that, but still.  I'd love to find a 50m reel for a tenner!
"What could possibly go wrong?"
Current Open Projects:  3 Channel Audio mixer with DAC, BT, pre-amps and h/phone amp, WS281x LED controller Version 2 5V/5A w/Atmega328, FY6600 Power supply, 5A DC Load (Still!)
 

Offline james_s

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Re: Buck or boost?
« Reply #35 on: February 01, 2018, 04:03:03 am »
That doesn't seem very expensive to me, especially compared to proper name brand clip leads. I used 18AWG wire from Hobbyking, I made a bunch of 1' leads and some 2' leads, only took a few meters of wire to make the whole pile of them.
 

Offline paulca

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Re: Buck or boost?
« Reply #36 on: February 06, 2018, 06:31:18 am »
Well I have 10 meters of 18AWG tinned copper silcone wire, which was about £6.99 for each colour.

I bought some croc-clips and soldered them onto 0.5m lengths.

My multi-meter can't measure the resistance of them, it flickers at 000.1 Ohm and the stablises at 000.0 Ohm. 

Job's a good en.
"What could possibly go wrong?"
Current Open Projects:  3 Channel Audio mixer with DAC, BT, pre-amps and h/phone amp, WS281x LED controller Version 2 5V/5A w/Atmega328, FY6600 Power supply, 5A DC Load (Still!)
 

Offline paulca

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Re: Buck or boost?
« Reply #37 on: March 10, 2018, 09:02:24 am »
Sorry to bump an old thread, but I wanted to give this little module credit where it is due.

https://www.ebay.co.uk/itm/262407885292

I thought I had not loaded it much, as I'd only been running it at 1.5A peak load.  It never faltered, never dropped it's voltage, never got hot.

Then I realised that I was measuring the 1.5A on it's input at 12V.  So  12V @ 1.5A = 5V @ 3.6A

It just works perfectly.  Does what it says on the tin, doesn't complain.  I have barely felt a bit of warmth from it and the inductor gets to be "warm to the touch", but that's about it.  To get it to pull 1.5A off a 12V input I have it charging my phone at 1.3A, and two ecigarettes at around 800mA each.  (I only have one USB current meter).  Input current is floating around 1.4A (currently) off my solar setup 12.4V.  Output voltage is 5.20V as always.
« Last Edit: March 10, 2018, 09:04:22 am by paulca »
"What could possibly go wrong?"
Current Open Projects:  3 Channel Audio mixer with DAC, BT, pre-amps and h/phone amp, WS281x LED controller Version 2 5V/5A w/Atmega328, FY6600 Power supply, 5A DC Load (Still!)
 

Offline bd139

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Re: Buck or boost?
« Reply #38 on: March 10, 2018, 09:31:41 am »
Some of those little Chinese buck and boost converter modules are pretty good. I've got one doing 4-5 amps quite happily doing boost from 12 to 24 volts! Think it cost just under £1.80 delivered from aliexpress.
 


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