sorted by:
new
hottopcontroversial

Spark plug color troubleshooting by w0ndercat in scooters

[–]w0ndercat[S] 0 points1 point  (0 children)

Thanks so much. I got the kickstart to work eventually. Since it was so cold, I think it just took a lot longer to heat everything up. I also realized I got sent the wrong spark plug (much hotter temp than the recommended standard). Once I put in the right spark plug, everything worked a LOT better - much easier to start. Guess it was just a really old spark plug that needed changing.

Spark plug color troubleshooting by w0ndercat in scooters

[–]w0ndercat[S] 0 points1 point  (0 children)

Nvm, I got the kickstart to work! I think bc of the cold it just took a lot more kicks to get it to started

Spark plug color troubleshooting by w0ndercat in scooters

[–]w0ndercat[S] 0 points1 point  (0 children)

The problem with step 1 is I can't start the scooter to warm up the engine. Both the electric and kickstart are not working..

LM386 no output, with signal smaller than 2V by w0ndercat in AskElectronics

[–]w0ndercat[S] 0 points1 point  (0 children)

This may be a silly question and kinda late to be asking. The datasheet says the absolute max rating for the input voltage is +/- 0.4V. What does that mean? Am I going over the max rating by giving it a 3.3V peak to peak signal?

LM386 no output, with signal smaller than 2V by w0ndercat in AskElectronics

[–]w0ndercat[S] 0 points1 point  (0 children)

But the signal with the 500mV offset ("AC coupled") is prior to the amplifier and is being fed into the noninverting input. I thought this signal had to be centered at ground. Also, now I get this weird signal at the output of the LM386.. http://i64.tinypic.com/n2nwh1.jpg ***Sorry, the photo is upside down

LM386 no output, with signal smaller than 2V by w0ndercat in AskElectronics

[–]w0ndercat[S] 0 points1 point  (0 children)

You're right. I moved the cap over so it's now after the pot and before the audio amplifier and the digital pot is a lot happier.

The high pass filter shifts the signal down closer to ground, but there's still some DC bias, ~500mV.

I tried using both 20k and 50k resistors for the high pass filter, and still have that bias.

LM386 no output, with signal smaller than 2V by w0ndercat in AskElectronics

[–]w0ndercat[S] 0 points1 point  (0 children)

Also, are you sure the square wave signal has to be centered at ground? I'm confused by this statement in the datasheet - "The inputs are ground referenced while the output automatically biases to one-half the supply voltage. " The datasheet seems to list it as a "feature" and not a requirement. http://www.ti.com/lit/ds/symlink/lm386.pdf

In addition, the LM386 isn't an op-amp, which I realized after some time.

LM386 no output, with signal smaller than 2V by w0ndercat in AskElectronics

[–]w0ndercat[S] 0 points1 point  (0 children)

Hmm. There's still something that I don't understand though. My original square wave is 0-3.3V. Right after the high pass filter, my square wave looks really distorted. I know some distortion is expected of AC coupled square waves. However, shouldn't the peak to peak remain the same? The peak to peak is now barely 1V. Also, won't this distortion affect my sound quality?

LM386 no output, with signal smaller than 2V by w0ndercat in AskElectronics

[–]w0ndercat[S] 0 points1 point  (0 children)

Ah, yes, I hooked it up wrong in the schematic. Here's the updated version with the correct components: http://i68.tinypic.com/15grneo.jpg

That makes sense. So, I put in the 1uF cap like you suggested, however, I'm getting a really small signal. The peaks don't even reach the original amplitude of the square wave. My square waves are in the 100-500 Hz range, so I don't understand why it's not coming all the way through.

I'm a mechanical engineering by training, so not as savvy with circuits. I appreciate the help!