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picaxe to LM386 LDR Vol control

Hi, i am using a LM386 ic to amplify the sound of a picaxe 28x2 ic.
This is the circuit i am using
http://www.hobby-hour.com/electronics/lm386-20.gif .
I can’t really hear much amplification of the sound, anyone have the same issue?

Also i was trying to swap the 10K V resistor for an LDR, so the volume would raise and lower with the influence of a LED brightness attached to a PWMOUT of the picaxe chip. I wired this circuit as i thought but it didn’t work. Does anyone know how to do this? And perhaps give me a circuit diagram?

At present the volume control of the 10K V resistor from min volume to max volume is only active over a very small amount of the 0 – 10K movement, over about 60ohms. This doesn’t feel right. Any thoughts???



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this is all on 4 x aa Rechargeables

... about 5v

oh yeah...thought i'd add that the speaker i'm using is a minature 1w 50ohm speaker.....20 x job lot from ebay for £13. good price i thought. ..so i need to make this works as i have potentially 19 other robots to make after this one and i still havn't done my first one yet, oh well it's a learning curve that i am quite enjoying.

50Ω you say? 1W? That's a bit bigger than I'd wager this circuit was designed for, what voltage are you running this all at?

these are the two circuits i tried but they didn't work. at the time i was just covering or illumination the LDR to see what happened, but nothing did. my end goal is to marry the LDR with a LED in a bit of tubing or heatshrink, the LED's brightness will be controlled via one of the picaxe pwmout, it's only wired link to the amp circuit will be that its on the same power.

any insights???


   i used one on my first robot but noticed I need a 100k pullup resistor on the input to get rid of noise. After that the volume control was no longer linier. I am driving 2 x 8 ohm - 2" speakers I slavaged from old main frames. Check out mini monster boe bot. I use Parallax Basic Stamp. Google LM386

im using a coil speaker. is there a circuit i can copy?

Can you post your circuit diagram including LDR and PWM, so we can check and maybe improve it?

LM386 should run without driver transistor on a (small) coil speakers.  You can increase the gain to 200 by adding one capacitor, see datasheet. I am using for my current project a simple one stage transistor amplifier, works well for me:



Is your speaker a coil speaker or piezo disc? If it's a coil speaker you may need to add a transistor or something on the output to provide it with more current.