ALeggeUp's Power Wheel Mod Build Log


#21

Just ebay, I’m still scared of alibaba :worried:. Plus it was only $3CDN, so something like $2.40USD


#22

I looked into this, but it seems a little advanced for me, I’m still not sure how many watts I need for a stereo and how many for a horn so I’ll have to do some experimentation. Once I know what I need I might be able to find something that would work, but I don’t think I’d be able to figure out if it is efficient or be able to improve it if it wasn’t.

In the mean time, I’ve got a 3W amplifier circuit I found on ebay and I’m working on a 15W version based on an app note

I find it curious the way they’ve separated out how the left and right are connected to power and ground, does this indicate that they should be physically separated somehow? or just showing what those capacitors are there for?

I captured it in a similar way on my schematic, but I realize during layout that it’s not going to make a difference. I’m thinking that there is something to this that I’m just supposed to know, but don’t.


#23

Usually it’s indicated like this because

  1. These are physically different nets
  2. The capacitors should be near a physical port for local decoupling. The capacitors act as a “charge bank” for that pin, which will likely need ready access to current when it’s quickly switching the FETs on and off (as happens in a class D amplifier)

#24

Does that mean closest to the power source or closest to the pin that it’s connected to?


#25

Normally closest to the pin


#26

Excellent, thanks! That makes sense.


#27

So would that be like a GND_L and GND_R that doesn’t connect to the main chip power?

Maybe I should just look at the datasheet for the PAM8124. :smirk:

Based on the app note though, that is how I see it? Kinda?


#28

I tried hooking up the mp3 player to the 3W amplifier board that I had and I was surprised by how loud it was, it was only pulling 10mA so definitely not 3W of power, but I don’t know if that’s what I should expect. It seems like 3W is loud enough for the speakers, but I’ll have to see if they still seem loud when it’s outside during the day competing with all the other sounds.