Failing at Circuits 101. Some help please.

[desmin88]

I'm going to build an Atari2600 portable, but I have a question about the 7805 regulator. I know I'm just being stupid and/or failing at Circuits 101.

Off of this guide http://forums.benheck.com/viewtopic.php?t=1148 at BenHeck and this picture.

So, to my understanding, you connect the positive terminal to Unregulated input.
Then you connect the regulated output to the Mobo.
Then you connect the ground to the atari ground.

What im confused is, where does the negative terminal come into play here?


Ugh, im going to read some electrical books or something.

Thanks

 

[Tibia]

The negative terminal of your power/batteries will also go to that regulator's ground. And the Atari's ground. Connect all of the grounds together, including the negative.

 

[desmin88]

So Positive to the Unregulated
Then wire the negative to the regular ground. Then put another wire on the regulator ground and attach it to the ataris ground.

Or am I missing something?

 

[Tibia]

Nope. That's it exactly. You might find it easier to solder two wires to the atari ground, then just one to the regulator, though. But you've got the idea now.

 

[desmin88]

Thanks!

 

[desmin88]

I made up a diagram of what I think would work. In this diagram I do understand there are more ground connections from the mobo but I didnt put them in here.

Thanks

 

[snowpenguin]

You only need one ground connection to the mobo.

 

[desmin88]

oh, so just one ground wire goes from mobo to the ground?

 

[snowpenguin]

Yes, the motherboard has a large ground plane on it that goes everywhere around the mobo.

 

[Tibia]

Forgive my lack of MSPaint skills.

I moved your ground over to the main motherboard, as that's where it is in the portable. This is how I've done it myself, though. My lack of a completed portable has more to do with an idiot neighbor than my work. lol

 

[snowpenguin]

idiot neighbor?

 

[Tibia]

Yeah. I had a worklog in the 2600 section. Tai killed the screen and the Atari. So glad he finally moved away.

 

[desmin88]

So you first wire the negative on the battery to the negative on the mobo, then at the same place wire to the 7805 ground?

 

[Tibia]

Yes. That's exactly how I did it.

 

[desmin88]

Great thanks!