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palcal

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Joined: 12/10/2011
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Posted: 01:34am 03 Apr 2018

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I have a small sound recording module that will record up to 120secs. It operates from 3v. When connected to 2x 1.5 volt cells it works OK. but if I connect it to my bench power supply it won't work. I tried 2 different supplies, no go but on batteries all is OK. I connect it up check with multimeter that there is 3v. and nothing happens?? Maybe some more filtering?
Paul.

"It is better to be ignorant and ask a stupid question than to be plain Stupid and not ask at all"

palcal

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Posted: 01:44am 03 Apr 2018

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Maybe I worded that a bit wrong. When I say I check with multimeter, there is 3v. on the module but it will not work.
Paul.

"It is better to be ignorant and ask a stupid question than to be plain Stupid and not ask at all"

VK2MCT
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Joined: 30/03/2012
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Posted: 02:31am 03 Apr 2018

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Are you sure polarity is OK ?
John.

palcal

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Posted: 03:11am 03 Apr 2018

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Yes polarity is OK I have two of these sound modules and both are the same, I have tried over and over I can't understand it. I checked my power supply on the scope and it is clean as a whistle. I do have another sound module, a different type from a different supplier and it is OK. I bought the problem ones from Oatley Electronics and have sent them an email.
Paul.

"It is better to be ignorant and ask a stupid question than to be plain Stupid and not ask at all"

TassyJim

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Joined: 07/08/2011
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Posted: 03:21am 03 Apr 2018

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Are you connected to anything else?
If so, there could be a ground loop doing something.

Jim

VK7JH
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Grogster

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Posted: 03:28am 03 Apr 2018

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What chip(voice recorder) are you using? So long as the PSU on the bench is regulated, there should not be any issues running it from that. Strange....

Smoke makes things work. When the smoke gets out, it stops!

greybeard
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Joined: 04/01/2010
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Posted: 03:29am 03 Apr 2018

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Have you checked the power while it is connected to the load?
And how close to the module can you check?
Sounds like a 'cu' problem to me (gap in the copper between the source and the load)

VK2MCT
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Posted: 03:36am 03 Apr 2018

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Do you have the earthy side of the PLAY/REC/ERASE switches connected correctly?

John.

palcal

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Posted: 03:50am 03 Apr 2018

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I am not connected to anything else PSU to recorder only, I check the voltage at the recorder + and - pins and have 3volts and it won't work. I connect to the batteries and all is OK. It is weird. I am doing everything correctly the other recorder from a different supplier is similar and it works OK.\
Paul

"It is better to be ignorant and ask a stupid question than to be plain Stupid and not ask at all"

WhiteWizzard
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Posted: 06:34am 03 Apr 2018

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Does your bench supply have a current limiter? If so; have you got it turned up to allow enough mA's!Edited by WhiteWizzard 2018-04-04

palcal

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Posted: 06:51am 03 Apr 2018

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Yes checked that. It's hard to believe but I can assure you it is happening.
Paul.

"It is better to be ignorant and ask a stupid question than to be plain Stupid and not ask at all"

Turbo46

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Joined: 24/12/2017
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Posted: 07:41am 03 Apr 2018

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Two new "1.5v" cells actually deliver 3.2 volts. Have you tried (say) 3.3 volts from the power supply?

BillEdited by Turbo46 2018-04-04

Keep safe. Live long and prosper.

palcal

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Posted: 09:07am 03 Apr 2018

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Yes I measured the battery voltage 3.16v. and set my PSU to 3.2v.
I will wait for the supplier to get back to me. They will have more of these and can test in their workshop.
Paul.

"It is better to be ignorant and ask a stupid question than to be plain Stupid and not ask at all"

matherp
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Posted: 09:43am 03 Apr 2018

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What is the part number?

Volhout
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Posted: 09:58am 03 Apr 2018

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Typically batteries are capacitors.
Especially when short wires are used, they can work as capacitors for the small electronics on the recorder.

You could try to add a 100nF ceramic cap across the power pins at the recorders circuit board, or a larger 100uF e-cap or both. That could work in combination with your bench power supply.

Success,

Volhout

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Turbo46

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Posted: 10:01am 03 Apr 2018

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Does your power supply have a slow voltage rise time? Does it have an output switch? Or have you tried a switch in series with the module? A slow rise time on the supply may cause the module to start in an improper state?

Bill

Keep safe. Live long and prosper.

Phil23
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Posted: 10:51am 03 Apr 2018

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palcal said Yes I measured the battery voltage 3.16v. and set my PSU to 3.2v.
I will wait for the supplier to get back to me. They will have more of these and can test in their workshop.
Paul.

Out of curiosity,

I wonder what would happen if you paralleled the power supply with the batteries.

PS set to say just 0.1 or so volts above the batteries so you don't jam a heap of current into them.

Phil

palcal

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Posted: 08:48pm 03 Apr 2018

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I tried a 100n cap, it also has a 47uF on board.
@Matherp
The only number on the PCB is APO6888 I bought it from here
Oatley Electronics

I will parallel the battery with my PSU later.
Paul.

"It is better to be ignorant and ask a stupid question than to be plain Stupid and not ask at all"

palcal

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Posted: 10:35pm 03 Apr 2018

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@Phil
I paralleled the power supply with the battery and it works ok. I tried increasing the power supply to 3.5v. When I press the play button I can hear a hiss from the speaker and an increase in current but it does not play, I press the record button which should produce a beep and nothing. Back to battery and it works perfectly.
As I said I have different module from another supplier that I am using in my project so I can continue but it is puzzling me.
Paul.

"It is better to be ignorant and ask a stupid question than to be plain Stupid and not ask at all"

palcal

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Posted: 12:28am 04 Apr 2018

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SUCCESS !!! The supply already has a 47uF cap on board across the supply. I put another cap of 100uF in parallel with it and it works, but still don't know why.
Maybe ripple current?
Paul.Edited by palcal 2018-04-05

"It is better to be ignorant and ask a stupid question than to be plain Stupid and not ask at all"

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