panel meter modification

[kiyoukan]

Okay so working on my lpm i read that certain panel meters can be moded to read different voltages, by changing a jumper and or resistor.
So i have some pics of the guts and was wondering who might know what i need to change to set it from 20v mode to 2v mode that way i get a higher resolution.
Thanks for any help!

Click link for pictures.
LPM pictures by kiyoukan - Photobucket
was reading this.
http://www.electronics-project-design.com/LED-Drivers.html
Does this look like it would help?

 

[JLSE]

It looks to have a jumper that you can move, mine had 'points' that had to be soldered
to jump..

Id imagine moving the jumper to the next set of pins will change the scale.
Did you not get an instruction with it??

You could also try searching the model #, im sure theres a topic somewhere...

 

[kiyoukan]

changing the jumper as the link i posted changes the decimal place.
i see something about turning the pot for the v ref and a resistor but i need help trcking it down if you know what i mean.

 

[JLSE]

"Since the maximum value which can be displayed is 1999, voltmeters with full scale readings of 199.9mV, 1.999V, 19.99V etc. can be made.The user must decide their own need. Then a reference voltage and maybe an input attenuator must be selected. To use the meter to measure 0 - 199.9mV the trimpot is adjusted so that the reference voltage between pins 35 & 36 is 100mV. And to set the meter for 0 - 1.999V, VREF must be set to 1.0V. Measuring higher voltages and nonstandard voltages will be discussed below. The relationship between full scale input voltage and the reference voltage"


From this I gather that you measure the voltage across pins 35 and 36,
adjust the pot until it reads 100mV. That should give the desired range.

Im not sure about R1 and C4, it looks to be only needed for the higher
range??

 

[kiyoukan]

so right now the voltage divider i think is set for a 100:1 ration or 1m resistor and a 10k resistor. if i want to set it to 2v i need to change it to 1m and 100k correct as well as set the trim pot.
I think i got this right?

 

[JLSE]

Looks right to me. RX stays the same and RY is changed.100k should
do the trick.

 

[kiyoukan]

but i still have to screw with the pot right?

 

[JLSE]

Yes but that shouldn't take more than a few mins..

Measure the voltage on the 2 pins, then turn till you
see 100mv..

 

[kiyoukan]

wait isnt 100mv if i want to set it to 200mv rand and the 2 volt range i have to set it for 1v right?
can you come one laser chat?
or got skype

 

[JLSE]

Sorry, watching UFC

If you have a working DMM, make all the changes
and test it. Just setup a 1.5v battery, verify its voltage
on a good DMM and adjust the panel til you see the
right numbers.

Probly save some time that way too...

 

[kiyoukan]

buwhahahah
i just replaced one of the resistors in the voltage divider with a pot and turned it till it read the right voltage.
it was at 20v now it read only 2v but has can now measure 5mw instead of 10mw min.
Who a nice cheap mod for the panel meter. its now a nice cool blue lpm.
Super small and sleek.
I am so happy!

 

[JLSE]

And my wife wonders why I scream 'ITS ALIIIIVE!!!' :eg:

Cant beat the fun of making things work as desired.