If I have a LED driven from a electronic VU meter, is there a way to have the led remain on (for approx 5 sec) when illuminated, then extinguish slowly (over approx. a 5 sec.period). So, in other words...when the led is illuminated by a audio level, it stays on, then slowly fades off. Like most of my requests, I know it sounds stupid...but it really does have a purpose. Thanks in advance
-- Kim..the man with a girls name, and Frankensteins body
Sure - a capacitor and a diode. It would be a rudimentary peak detector - the diode allows the current that lights the LED to charge the capacitor as well, and when the signal decreases, the only discharge path for the cap is the LED and its current-limiting resistor.
Good Luck! Rich
-- 1. From your post, I assume that you want the LED to stay fully illuminated while the VU meter is indicating audio and then, when there is no audio, you want the LED to stay illuminated for 5 seconds and then to fade to black in another 5 seconds. Is that right? 2. Is one side of the VU meter connected to ground?
-- As usual, you\'re full of shit. Wanna know why?
-You are correct in my assessment of the needs
-Yes it is connected to ground on one side of the displays
-I came across this schematic, although its supposed to fade incandescent over a VERY long period of time. What do you think? [URL=
Sorry, that's:
have
stays
have
I know! I know!
There's no 555 in it.
Looks like it is designed to flash a lamp on and off for a period of time . . . just from looking at the schematic - I could be wrong. Do you intend to build one of these circuits for each led in the display?
Peak and Hold . . . that sort of thing is usually designed into the chip - it is a hassle to build it from discrete analog parts.
Peak and Hold is in the books - - - take that circuit and have it pulse the bargraph display circuit with the peak and hold voltage? 50% of the time the bargraph display follows the signal, the other 50% it displays the (current/real time) peak voltage. Continuously switching between the two levels. Your eyes will see the bargraph moving and the peaks will stay illuminated longer.
As far as a cheap and dirty cap and diode . . . I don't think so. Each LED would have the circuit and each led would stay illuminated once it was turned on.
Peak and Hold - and multiplex the signal input to the bargraph display circuitry - that could be made to work.
----== Posted via Newsfeeds.Com - Unlimited-Unrestricted-Secure Usenet News==----
----= East and West-Coast Server Farms - Total Privacy via Encryption =----
...
Easy- he's Rich, but Drunk... oh wait, it's just plain Rich... well it's all the same. 8oP
Tim
-- Deep Fryer: a very philosophical monk. Website: http://webpages.charter.net/dawill/tmoranwms
-- Nuh-uh... It\'s threefold. 1st fold, you won\'t be able to get the response the OP wants with a simple diode-cap intregrator, 2nd fold, there won\'t be enough power coming into the VU from the audio signal to make the circuit work. 3rd fold, the circuit will screw up the response of the VU meter.
The link you pointed to is a basic PWM control. LM324 sections 1 and 7 generate a triangle wave which is presented to amplifier section 14 used as a comparator. The 3300uF cap is initially discharged and will cause a nearly 100% duty cycle to drive the lamps. As the capacitor charges, its voltage compared against the sawtooth causes the PWM to decrease to zero (lamps dimmed to black).
May I recommend that when you post a link, don't put it in brackets. Also leave a space after the link. This allows readers to auto detect a link.
[URL=
...
Because you're John Fields, and have a chip on your shoulder?
Thanks, Rich
--
Please bottom post.
I think this will work for you: (view in Courier)
+12V>---------+--------------+-----+-------+--------------+
| | | | |
| | | | [510]
[10K] [1M] | | |A
| | | | [LED]
| +--[10M]--+ |R2 | |
|R1 | | [10K]----+-----|------|+/ | C
IN>--[100K]---|------|-/U1A | | U1B| |+ |
| LM393 |+ | | [22µF] |
| [10µF] | | |C2 |
| | | | | |
GND>----------+--------------+-----+-------+---+----------+
Adjust R1 to determine at what input voltage the circuit triggers
ON, adjust R2 to set the delay before dimming starts and select C2
to give you the dimming timeout you want. Wth 22µF the LED current
goes from 20mA to 2mA in about 5 seconds.
-- Nope. Whether I had a chip on my shoulder or not, you\'d still be full of shit. Guess again?
I think it was ripped off my website at:
You will get more information there with several alernatives using both LEDs or incandescents.
Thanks,
-Bill
Yes, it's ripped off from my website. Original is here:
-Bill
Don't you think that "ripped off' is a bit of a strong statement. If a circuit is made available for the world to see, and therefore used as an example (as is the case is here) is that ripping it off? Kind of a old....and outdated way of thinking of things...isn't it. By the way....I have to say that Bill Bowdens schematics circuits page is well designed, and quite useful. I often refer to it.
No.
Yes, and it's not an example. It's a unique work of art that belongs to the author, and anybody that copies and reposts it somewhere else without permission is a thief.
-Bill
Hi Bill,
looked at your red eyes fading circuit and was wondering about the reverse bias on the electrolytic cap. Is that OK to do indefinitely?
regards
IanM
Yes, it should be allright with 1 or 2 volts reverse. That circuit charges the cap backwards to about 1.5 volts. But if you are worried about it, you can use 2 larger caps back to back. Or, you might make it work using a non-polarized 2uF cap and somewhere around 1 meg in place of the 47K.
Here's some data on electrolytic caps.
-Bill
ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.