LM3915 ampmeter

[macobt]

Hi to all
How I can measure the curent with leds(LM3915)
I need schematic how to build,measureing will be maxium to 1500mAh

 

[user_88]

It seems like you could get a regular current shunt, or a very low value resistor .... maybe 0.01Ω, and insert it in series with the current source that is to be measured.
Then get an op amp and amplify the voltage generated across the resistor/shunt.
When you get a reasonable voltage from the output of the op amp ... maybe 2 volts .... you can connect the LM3915 to this port, and have the leds turn on in a manner that is proportional to the voltage across the resistor.

You might want to look at the LM3914, which is the linear proportioned version of this IC.

If your intended purpose is for instrumentation or a specific purpose, you might want to get a manufactured and calibrated current shunt .... or at least some sort of precision resistor.

 

[macobt]

hi user 88
J want to monitor tne power suplay wheh I draw curent up to 1500mah from him,too see on led amp meter,schematic will be good to explain me how to do it.
regards
macobt

 

[user_88]

hi user 88
J want to monitor tne power suplay wheh I draw curent up to 1500mah from him,too see on led amp meter,schematic will be good to explain me how to do it.
regards
macobt

.... I will take a look at it ... but really need to get a simulation going before I can make any definite recommendations .... check back ....

 

[user_88]

I ran a simplified input simulation, and the amplification of the resistor shunt voltage is feasible, using an op-amp with only one power supply, if you choose the correct op-amp. An LM 358 or an LT1013 seems to work adequately. The op amp is set up in non-inverting form, with a gain of about 100. That is, the Rf resistor is 10k Ω, and the Rin resistor is 100 Ω.

Haven't linked the LM 3915 chip yet. ... Will try to have some sort of diagram later.