LED flasher to music (needs improving... transistor help)

[madmikejt12]

hi, i have made a set of speakers with a battery powered amp and added some LED's that flash to the music, however, they only come on when the music is loud and muffled, i would like to make a small circuit to boost the current or voltage (dont know which one)

first off, will i need to boost the current or voltage? i thaught it would be the current.... secondly, i have 2 o/p's from the chip (+/-) and 2 wires going to the LED's (+/-) so, i need something in-between, could i leave the - joined together and add a transistor to the + side only, so i have:

O/p from chip (+) - Base of transistor
LED's (+) - Collector of transistor
negative (from chip) - Emittor of transistor

Would that work?
Thanks in advance,
Mike

 

[akg]

are they just blink according to the music.? , then u need a simple CE amp design , with Rc as LED and keep it just lit.

or if u need bar/dot graph type pls see lm3914/5 etc.

 

[madmikejt12]

i have an amp using the lm386, it amplifies the signal, which is sent to speakers and leds, the speakers are fine, its just when i don't want my music loud, i dont see the lights, i was wondering if i could add a transistor circuit with a pot (to control sensitivity and not the volume) in between the amp and the LED's to boost the current or voltage of the signals ONLY for the LED's

Thanks,
Mike

 

[audioguru]

You could add a compressor circuit which automatically reduces the signal's gain to the LED when the signal is loud, and increases the gain when the signal level is low:

 

[madmikejt12]

thanks for that, what is the LDR for?


Is there a simpler circuit that just increases the current or voltage and i can use a pot to manualy adjust the increase of current/voltage depending on how loud i have it?

Thanks,
Mike

 

[audioguru]

thanks for that, what is the LDR for?

It is part of the automatic volume control.

Is there a simpler circuit that just increases the current or voltage and i can use a pot to manualy adjust the increase of current/voltage depending on how loud i have it?

Why not use your audio amp for audio and make another circuit just for the LED? Then the LED will always show the music without being affected by how loud you have your speaker. Both amps have their own volume control and connect to the music source:

 

[madmikejt12]

i'll try that again, i was trying to avoid doing that because i tried thar circuit for ages, it worked on the breadboard but when i soldered it, it didnt..... i gave up in the end and baught the ready made one: **broken link removed**

 

[audioguru]

My 2nd circuit to drive 2 LEDs is extremely simple. It should work fine and do what you want.

 

[madmikejt12]

i tried the 2nd one... no luck i think i'll but another amp module lol

Even if i do get it working on the breadboard, its not going to work when i solder it!!! lol

 

[Dr.EM]

Soldering shouldn't be a problem for this. What kind of iron are you using, does it solder well? I used to use a 30W cheap iron, and nothing worked using that; as soon as I switched to an 18w Antex one, everything has gone smoothly. Stripboard is ideal for assembling things like these (I made this circuit a while back for use as a headphone amp), just remember to break the tracks under the IC, and I find IC holders help.

 

[madmikejt12]

sounds like your old one!!! its a cheap one and the tips keep burning away after 3 hours of total use!! it only works if you hold the solder in a certain place on the iron.

 

[Dr.EM]

Ah, i'd definately advise pending some money on one like this:

**broken link removed**

Thats what I use now, looks like its reduced at the moment too

I use this solder with it, it gives good results:

**broken link removed**

 

[madmikejt12]

thanks i was actualy thinking about getting a similar antex iron it could have been that one, not sure though..... that is the solder i already have, so no problems there thanks

 

[audioguru]

Hi Dr. EM and mad Mike,
The max temp of the 18W soldering iron is only a little more than my Weller temperature controlled 34W iron. Since mine has more power then I can solder bigger things longer.

An important recommendation for soldering irons is to keep the tip clean and tinned. My Weller tips come tinned and stay tinned. I wipe the hot tip in the grooves of a clean damp Weller sponge before each solder joint or two. I rinse the sponge daily. I think the sponge is a natural one (from the sea). Whenever I try making a solder joint without my damp sponge then the joint is lousy.

 

[Nigel Goodwin]

Whenever I try making a solder joint without my damp sponge then the joint is lousy.

Interesting?, I make perfect soldered joints without using a sponge - I perhaps dampen it every few months (if it's lucky!) :lol:

I would find it very difficult to make a 'lousy soldered joint'.

Incidently, Antex bits are iron plated, and should be tinned AS they first warm up - they last for years in normal hobby use.

 

[DigiTan]

Sorry if this isn't 100% relevant, but what does the 10uF capacitor do in the "microphone input" circuit?

 

[audioguru]

Hi Digitan,
The 10uF cap across pins 1 and 8 0f the LM386 boosts its gain from 20 to 200 so it is sensitive enough for a microphone.

 

[madmikejt12]

i find the silver stripboard better, even with this iron, i can make good joints, its almost as if the solder is attracted to the tracks whereas on the other one it seems attracted to the tracks and the other strips!!! this could be because i dont sand it to remove any grease or that it is at least 8 years old!!!!

 

[madmikejt12]

i was looking for something simple like this: https://www.st-andrews.ac.uk/~www_pa/Scots_Guide/audio/part1/page2.html (fig 1.5 on the left) i tried it but it didnt work, the red LED came on but none of the others, the red is the most sensitive (probably because it needs slightly less voltage than the others)

 

[madmikejt12]

also, the transistor was getting hot