Recent content by NipunaG

Hi everybody. I'm an electronics hobbyist and use Ferric chloride to etch copper circuit boards. I'm left with a solution of copper chloride (or is it cupric chloride? Chemistry isn't my forte). So my question is, how do I dispose of it? I already searched around on the internet and there was no...

hi everybody. a friend of mine needs to make an ammonia sensor from the mq137 sensor, but we couldn't find a circuit anywhere. can any of you guys help us out? we need it to trigger a relay when a preset threshold is reached. thanks in advance!

All right guys! it's working :D. It was just a bunch of resistors in all the wrong places. lol. (I'm so sticking up the resistor color code on my wall now!). Thanks guys. @Jim I don't know where you could get one where you live (I'm from sri lanka), I got mine from some local shop long ago...

Yup. it's doing 10+ volts all right. But, the resistor is already a 4w one and I'm using a factory made (or whatever they're called) PCB i.e.- not one I made. that came with a specifications sheet with everything like the transformer voltage, component values etc. mentioned. I just noticed...

This would be the schem. (minus tone control and lb1405 led meter) I also noticed that the voltage across the smoothing caps is 21.x (transformer is 28-0-28) but i guess its that resistor dropping a large percentage of the voltage across itself.

no. it's the one across pins 4 and 7. P.S- I just realized that it's working properly for about one second on turning on before the volume drops to the sound output level of a headphone. BTW thanks for replying :)

go for less turns/ thick wire (less resistance therefore high current). The thicker and shorter a wire, the lesser its resistance.

why not the IR system?

Thanks. It's clear now.

STK 4191 amp. burning resistor :( I just built a STK 4191 amp. when i supply power a 100Ω resistor (1w) near the IC starts smoking. there're no short circuits across the ICs pins or anywhere on the board and i took all precautions when soldering the IC on (was done with heatsink + 40mm fan...

Hello everybody. I'm interested in this field too and would like to know how these transmitters work. From what I have learned, fm transmission is done by "piggybacking" the audio signal onto a radio wave. In this circuit, where does this pure radio wave come from? does simply having a...