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Breadboard power supply decreasing voltage


DavidL
(@davidl)
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Hi,

I recently purchased some breadboard power supplies and I'd appreciate any guidance about whether or nto I'm using it correctly.

 I plug the power supply into a breadboard, and connect a 9v battery, via the barrel connector. to the power supply.  I have a couple of wires connected to the breadboard and to a multimeter.  When I measure the voltage with a multimeter, it starts at the expected value, but gradually decreases.  Within about a minute it drops by about a volt or more.

If I connect the same battery (connecting with wires instead of a barrel connector) to the breadboard, the voltage shows about 9.2 volts and is stable.

I've tried with several different power supplies, different batteries, and different connectors between the battery and power supply.  The voltage would start at the expected (5.5v or 3v) voltage, but it would decrease by about 1 volt or more within a minute.

I had assumed the voltage would be steady with the power supply.  Was that incorrect?  Am I doing something wrong?

 

Thanks.


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Ron
 Ron
(@zander)
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@davidl I just tried 2 of those breadboard power supplies, and the voltages stayed constant. You should make sure you have a fresh 9V battery. Maybe put the test leads on the battery itself with nothing else connected to vet the battery. Also, do you have access to a different meter?

At this point you have at least 3 variables, battery, power supply, meter. Swap one at a time and see which one the low voltage follows.

It is considered poor judgement to traverse a chasm in 2 leaps.


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DaveE
(@davee)
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Hi Davidl,

   It is difficult to diagnose at a distance, particularly as you don't say how much current is flowing.

Assuming your power supplies are of the type using an AM1117 or similar linear regulator,  two possibilities come to mind:

  1. The current demand is such that the voltage regulator is getting hot, and going into a protective shutdown.
  2. The battery voltage under load is falling .. I am not clear of the conditions when you measure 9.2V.

I would measure the actual voltage on the input and output pins of the regulator chip, using the ground connection pin on the regulator (assuming it is a fixed voltage one) or a ground point, as close as you can get on the power supply PCB, if it is a variable voltage one. If the input voltage is less than you expect (presumably about 9.2V), trace back to find a reason, including possible problems with plugs, sockets, etc., as well as a tired battery.

Also check the temperature of the regulator .. although the data sheet may suggest otherwise, the outside of the package will be a lot cooler than the silicon chip inside ... if it is 'too hot to touch', then it is too hot!

Good luck, Dave


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Ron
 Ron
(@zander)
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@davee From his description I took it to be a no-load situation. My bet is tired battery or defective meter. I was testing with 6 rechargeable NiCads yielding 7.86 volts.

It is considered poor judgement to traverse a chasm in 2 leaps.


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DavidL
(@davidl)
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Posted by: @zander

@davidl I just tried 2 of those breadboard power supplies, and the voltages stayed constant. You should make sure you have a fresh 9V battery. Maybe put the test leads on the battery itself with nothing else connected to vet the battery. Also, do you have access to a different meter?

At this point you have at least 3 variables, battery, power supply, meter. Swap one at a time and see which one the low voltage follows.

Hi Ron, thanks for the response.  It's good to know that I should be seeing steady voltage.  

I should have mentioned that I've tried with two batteries.  They were both unused, but they may have been sitting for quite a while  (possibly years) before I opened the package.

The multimeter shows 9.2v when connected to the terminals of the battery.  It also shows a steady 9.2v if I connect the battery directly the breadboard (like this) and connect the multimeter to wires connected to the breadboard.  

I only have one multimeter, so I'm going to order a second one.  I'll probably try a fresh pack of batteries too.

Thanks.


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DavidL
(@davidl)
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Posted by: @davee

Hi Davidl,

   It is difficult to diagnose at a distance, particularly as you don't say how much current is flowing.

Assuming your power supplies are of the type using an AM1117 or similar linear regulator,  two possibilities come to mind:

  1. The current demand is such that the voltage regulator is getting hot, and going into a protective shutdown.
  2. The battery voltage under load is falling .. I am not clear of the conditions when you measure 9.2V.

I would measure the actual voltage on the input and output pins of the regulator chip, using the ground connection pin on the regulator (assuming it is a fixed voltage one) or a ground point, as close as you can get on the power supply PCB, if it is a variable voltage one. If the input voltage is less than you expect (presumably about 9.2V), trace back to find a reason, including possible problems with plugs, sockets, etc., as well as a tired battery.

Also check the temperature of the regulator .. although the data sheet may suggest otherwise, the outside of the package will be a lot cooler than the silicon chip inside ... if it is 'too hot to touch', then it is too hot!

Good luck, Dave

Hi Dave,

Thanks for the help.  The power supplies are  "HiLetgo", not sure if that is the type you're describing or if that's enough information.  Hopefully this image will work.

The 9.2 v was measured when the multimeter was connected to the battery terminals, and also when the battery was connected directly to the breadboard (e.g. this) and the multimeter was connected to the breadboard.  Nothing else was connected to the breadboard when I made those measurements.

I didn't notice any heat when I removed the power supply.  

I'm going to buy some fresh batteries and see if that does the trick.

Thanks!
  


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DavidL
(@davidl)
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Posted by: @zander

@davee From his description I took it to be a no-load situation. My bet is tired battery or defective meter. I was testing with 6 rechargeable NiCads yielding 7.86 volts.

Ron, thanks for the response.  I'm going to get new batteries later today.  The batteries I tried were unused, but they could be years old.  I'm also going to get a second multimeter.  Seems like it would be useful regardless of what happens with this.

Thanks!


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Ron
 Ron
(@zander)
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@davidl Excellent troubleshooting technique, so rare and refreshing. The batteries are for sure suspect, the multimeter can't be eliminated without a tie breaker. The direct connection of 9.2V is under no load so that voltage doesn't mean too much. The chances that you have several bad power supplies is not impossible but highly unlikely. The power supplies do present a little load on the batteries so a weak battery could be affected. Now that I wrote this I am more sure it's the battery. BTW, you can use anything for a battery as long as it isn't over about 20V, I have a rechargeable battery pack of 6x1.3V and a lantern battery, they all work as the voltage regulator has a wide tolerance. Good luck.

It is considered poor judgement to traverse a chasm in 2 leaps.


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Ron
 Ron
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@davidl If you are committed enough to warrant the expense, one of those meters with clamp on ability would be a good second meter. The USA made versions are pricey, but the clones are more reasonable. I got mine because I was installing a solar system but the average person doesn't need one. Also I am a tool guy.

It is considered poor judgement to traverse a chasm in 2 leaps.


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DavidL
(@davidl)
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It was the batteries!  I tried two and thought that was enough.  Next time I'll try three.  

The two batteries that I was using initially were from the same package.  I found another package of batteries, replaced the problem batteries, and the voltages have been steady for over 5 minutes (vs about 15 seconds before).

Thanks for the help everybody!


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DavidL
(@davidl)
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Posted by: @zander

@davidl If you are committed enough to warrant the expense, one of those meters with clamp on ability would be a good second meter. The USA made versions are pricey, but the clones are more reasonable. I got mine because I was installing a solar system but the average person doesn't need one. Also I am a tool guy.

Ron,

Could you recommend a specific meter or brand?  I searched for multimeters with clamp on ability, and the prices ranged from about $30 to over $400, so I'm sure there are some factors that I should consider.

I would like to get something good if it's not too expensive.

Thanks.


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Ron
 Ron
(@zander)
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@davidl I just did an amazon search on 'clamp meter' something in the $30 to $40 will do, just look carefully you will see the same meter from different suppliers for different prices. The one I got is no longer available.

It is considered poor judgement to traverse a chasm in 2 leaps.


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DavidL
(@davidl)
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Joined: 4 months ago
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Posted by: @zander

@davidl Excellent troubleshooting technique, so rare and refreshing. The batteries are for sure suspect, the multimeter can't be eliminated without a tie breaker. The direct connection of 9.2V is under no load so that voltage doesn't mean too much. The chances that you have several bad power supplies is not impossible but highly unlikely. The power supplies do present a little load on the batteries so a weak battery could be affected. Now that I wrote this I am more sure it's the battery. BTW, you can use anything for a battery as long as it isn't over about 20V, I have a rechargeable battery pack of 6x1.3V and a lantern battery, they all work as the voltage regulator has a wide tolerance. Good luck.

Thank you for the kind words!  I'm enjoying learning and experimenting (for me, swapping out parts is still an "experiment").  It's great to have the people on this forum as a resource!


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DaveE
(@davee)
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Hi @davidl,

  Good to see you tracked the problem down.

  Yes, the regulator boards were of the type I had in mind ... there are a lot of slightly different variations around, but they are all basically similar.

FYI the actual regulator parts are almost certainly the two parts near the top at the centre of the board, with three pins on the top side and a wide pin on the bottom. This is a link to the type of part typically used on these boards and elsewhere: http://www.advanced-monolithic.com/pdf/ds1117.pdf

Best wishes and good luck with your future products.

Dave


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