Low cost, Small, 10ma output, 12v to 16v dc in.

I want to use Harbor Freights free Meter for numerous applications.
Did I just hear a Chick, or was that the sound of the word Cheep.
Mostly for prototyping new Projects.
Thanks for any ideas.

 

How about 9 V batteries? At 10 mA, they will last quite some time, probably 40 to 50 hours of use.

What does using a Harbor Freight meter have to do with the question?

Are you trying power these meters from an external source?

 

Define "low cost"
Define "small"

Have you ever used the search/filter functionality on electronic component site suppliers like Digikey, Farnell/Newark , Mouser,etc...?

 

Are you trying power these meters from an external source?

Yes. and they will be on for years during testing.

Have you ever used the search/filter functionality on electronic component site suppliers like Digikey, Farnell/Newark , Mouser,etc...?

Yes, I get most of my stuff from Digikey Most EBAY stuff is from China

 

What about one of these?

 

Yes. and they will be on for years during testing.

Okay. So what are your other requirements?

What is the border at which something is no longer "low cost"?

What is the border at which something is no longer "small"?

 

Yes. and they will be on for years during testing.



Yes, I get most of my stuff from Digikey Most EBAY stuff is from China

Why don't you just use a AC->DC 9V Wallwart?

Don't knock China, they have a lot of incredible vendors there that sell quality stuff that you can't even get in this country. And it isn't junk.

 

Yes. and they will be on for years during testing.



Yes, I get most of my stuff from Digikey Most EBAY stuff is from China

Do the meters you plan to use have an auto power off function? Every meter I've used in the last twenty years or so has had that function. If yours do, then they won't be on for years during testing!

 

Do the meters you plan to use have an auto power off function? Every meter I've used in the last twenty years or so has had that function. If yours do, then they won't be on for years during testing!

The Harbor Freight ones don't.

 

Here is a link to my solution:
https://forum.allaboutcircuits.com/...anel-meter-no-transformer.118110/#post-929539

 

Here is a link to my solution:
https://forum.allaboutcircuits.com/...anel-meter-no-transformer.118110/#post-929539

Thanks Will Breadboard it and try.

 

Thanks Will Breadboard it and try.

A couple of comments...
First, the circuit was designed for 5 volts in. If you use 12 volts, the output voltage is probably too high for your typical meter. It may even damage it.

Second. If you use a CMOS 555 timer, I think it can power several meters. The meter I tested drew way less than 1 mA. Keep in mind that you need one copy of the circuit per meter otherwise the measurements will interact.

 

First, the circuit was designed for 5 volts in. If you use 12 volts, the output voltage is probably too high for your typical meter. It may even damage it.

Thought of that too. Should be able to drop it to 9v with a resistor divider.
Should be able to Drive 5 Ckts with one 555 chip.
Need 5 meters.
Thanks again

 

Thought of that too. Should be able to drop it to 9v with a resistor divider.
Should be able to Drive 5 Ckts with one 555 chip.
Need 5 meters.
Thanks again

In general, using voltage dividers in power circuits does not work well. The problem is that the load is not well known or it varies.

I would use an LM78L5 voltage regulator to get a solid 5 volts for the meter circuit.

 

How about a 9v zener the battery in the meter is 9v

 

How about a 9v zener the battery in the meter is 9v

That and a 4.7K ohm current limiting resistor. It would be a bit of a pain to do it in every meter, though.
A single 5.1 volt Zener and 680 ohm current limiting resistor would work for making 5 volts for the CMOS 555 circuit. But, I still prefer an LM78L05.

p.s. Don't forget power supply bypassing for the 555.

 

Well, test results were not so good.
See attached Diagram of the actual ckt.

Why don't you just use a AC->DC 9V Wallwart?

I never thought of using one of them, I have many in the junk pile.
It did not work either, the meter reading was very erratic jumping from 15v to 0v testing the battery.

Looks like I will stick with the batteries.
I'm in a very noisy environment 8 modified sign-wave inverters come on alone or together at various times.
don't know if that's it but it could be why the AC->DC converter did not work.
BTW, I was using power off the Grid to power the converter not the Modified sign-wave power.

 

Re: Using a wallwart.

I never thought of using one of them, I have many in the junk pile.
It did not work either, the meter reading was very erratic jumping from 15v to 0v testing the battery.

What kind did you use?
Did it put out a regulated 9Vdc?

 

Re: Using a wallwart.What kind did you use?
Did it put out a regulated 9Vdc?

Transformer type, Not regulated, 9v DC, it put out 15v DC.
I regulated it at 9 volts with a resistor and zener diode at the meter.
I also hooked it to two different bench power supply's, same results with both supply's.

 

Transformer type, Not regulated, 9v DC, it put out 15v DC.
I regulated it at 9 volts with a resistor and zener diode at the meter.
I also hooked it to two different bench power supply's, same results with both supply's.

I'm inclined to say you're mis-using the wallwart, or it's defective. All such devices (in fact, any device that provides power) is designed to provide a regulated voltage within a range, based on an expected load or range of loads. A meter doesn't provide sufficient load.

Likely your 9V wallwart is just fine.

However, what would really be nice is if you told us a model number, or provided a link to this 'meter' you're referring to from HF, so we could look at it, and obtain specifications. It could be that you're completely misusing it.... just a thought.