LEDs VU meter with no external power

Why not use a classic analog needle-meter type VOM or VU meter?

You can still buy meter-movement VOMs, like at a hardware store.

John

LCD panel. Can't beat the power savings. You can probably steal some power and run in less than 1mA, including the controller.

What drives the LCD panel ??

some sort of controller will need to be used here, or did I miss the OPs question. :-\

don

ome

Yes, a low power controller can run below 1mA. LCD itself does not take much current (uAs).

Dead easy. Take your row of LEDs, add an asortment of zeners to give differing V_on levels, and add a transistor current limit to each one. Add a diode on the lot. Job done. It wont distort as long as its run from low impedance, which is normally the case.

NT

Use a conventional d'arsonval meter designed for VU operation (eg: a VU meter; correct damping)..

That is too complicated..

Linnix is suggesting something that has no real solution.

Linnix, You are suggesting that this circuit steals some power from the audio channel to power the circuit.

Do you have any links on how this can be done ?

don

Hi guys, sorry for late reply. thanks a lot for your answers.. I don't know why someone started out the lcd thing, is not really what I had in mind. What I need is a simple row of leds... I just have no idea how they could steal power from the speaker cable. This is a kit that does the job, but it's in the US and it would take me ages to get hold of one. I wrote to the people, but they didn't seem open to share their schematics.

Thanks a lot, this forum is soooo good!

Hi there, this sound like what I was trying to do.. but I am not a real exp= ert and I'd have no idea on how to this! HAve you done this before? have yo= u got a schematics or some pictures, so I can understand better? sorry to a= sk man, but i really have no idea where to start from! :)

look at the enlarged image, I think the circuit is PASSIVE just a couple of LED-resistor combination, the price is aligned!

This is not a forum is the "Usenet News" !

Yes, What do you mean passive? maybe it's exactly what I need! but I really have no idea.. i wish i knew more!! I also found another one, which is crazily expensive toh:

:)

have no idea.. i wish i knew more!! I also found another one, which is crazily expensive toh:

is passive in the sense that there isn't no transistor or operational amplifier in that circuit just a couple of leds with series resistor, ad hoc selection of the resistors values let the leds lit on differents voltages ( I think ;-) )

the velleman kit have the full schematic on the manual, you can mount it on a "scheda millefori" ( prototype board ) buying just the components

BTW exists it.hobby.elettronica where you can speak in italian language

I live in england so I don't really need to speak italian, also the other guys involved in this project don't speak italian so it wouldn't help much. but yes, thanks for the link... sei italiano?

Yes I know it's just a series of leds and resistors, that's why it was perfect for us. damn easy! But I guess not that easy for me. I guess I just need to learn more about electronics, unless someone would find a schematic for it.

thanks

guys involved in this project don't speak italian so it wouldn't help much= . but yes, thanks for the link... sei italiano?

rfect for us. damn easy! But I guess not that easy for me. I guess I just n= eed to learn more about electronics, unless someone would find a schematic = for it.

The schematic is on the velleman page linked to. Help yourself for once

What? did I upset you for some reason? I am really sorry if I did.. anyway I meant the schematics for the simple one, the one that uses just leds and resistors..

sorry if I am not an expert. maybe I just choose the wrong group.. ?

and resistors..

I think if you looked at the schematic referenced in that document, even a beginner would get what needs to be done.

Compare the photo of the simple with the schematic.

Its really not that hard.

Speaker lead 1 -------/\/\/\/\/\--------|

involved in this project don't speak italian so it wouldn't help much. but yes, thanks for the link... sei italiano?

hops, sorry I have not checked from where you posted and yes, I am italian, my name is Marco

for us. damn easy! But I guess not that easy for me. I guess I just need to learn more about electronics, unless someone would find a schematic for it.

I think that there in nothing simpler than the two circuit, the price of the first kit is almost unbeatable, the velleman kit GIVE you the schematic with component valueson the last page of the manual, you just need some soldering skill to replicate the circuit

the schematic for the first kit is something like this ( only 3 led shown ):

IN--->|---+----+----R1----LED----+ | +----R2----LED----+ CCC +----R3----LED----+ | | IN--------+----------------------+

->|- is an 1N4148 diode CCC is an electrolytic capacitor ( 10 microF ? ) LED is a led R1 - R3 are the series resistors they MUST be selected to allow the led to lit at selected input voltages ( at least 1mA of current on led

ome

Yes, it is. But it's doable and also OT, i guess. It's a single chip LCD controller with A2D.

We use it to monitor a 12V battery, and not draining too much power from it. The micro also monitor it's own power divided from 12V into range of 3V to 5V. If voltage is low, it goes into deep sleep with LCD on (around 100uA). If voltage is OK, it samples the main 12V as well as other signals. Even in this active mode, current is around