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Author Topic: electronics problem involving pics, 64 leds and lots of hair  (Read 2004 times)

bigal

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electronics problem involving pics, 64 leds and lots of hair
« on: September 17, 2004, 11:23:16 AM »

Hi, i have just finnished prototyping the picxie2 circuit here:
http://www.zws.com/products/picxie2/index.html
but am failing to get it to work, the pic gets hot but thats all, i have rebuilt on breadboard twice, but cant find the prob, i was wondering if anyone could spot any issues. I am using blue LEDs so i didnt use resistors on them since the circui runs on 3vdc and the LEds are 3.3v.
I tried running this on my multivolt transformer, with a voltmeter connected, and it went from 3.5v 'ish down to 0.8v when connected... with no sparks when connecting or warm wires, the PSU can chuck out 5amp, which should make the wire GLOW if its dragging that much current, anyway, pics here:

http://www.hellzbellz.net/screen_dumps/picxie/

EDIT
is it me or is the batt symbol on that schematic the wrong way round?

IS VSS ground..

If so i need 2 new 74HC374's and nother pic from my box.

STUPID DAMN BATTERY!!!!
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Greggyboy

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electronics problem involving pics, 64 leds and lots of hair
« Reply #1 on: September 17, 2004, 11:54:55 AM »

Yep, looks like Vss is your ground. The battery looks right to me. Someone correct me if i am wrong.
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viridius

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electronics problem involving pics, 64 leds and lots of hair
« Reply #2 on: September 17, 2004, 01:41:05 PM »

Vss is the ground.  If you want to use the blue LEDs, run the whole circuit off of 5 volts and use the appropriate resistors.
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Skylined

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electronics problem involving pics, 64 leds and lots of hair
« Reply #3 on: September 17, 2004, 03:26:34 PM »

Vss = Ground
Vcc = Positive
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bigal

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electronics problem involving pics, 64 leds and lots of hair
« Reply #4 on: September 17, 2004, 03:38:26 PM »

Action to be taken by me:
New chips, looks like i must of screwed those there,
All circuit run of 5/4.5V (3xaa batts) with **ohm resistors on LEDs

Looks like another order for farnwell, rapid and maplin... ;)
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linear

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electronics problem involving pics, 64 leds and lots of hair
« Reply #5 on: September 17, 2004, 08:49:12 PM »

Quote from: Skylined
Vss = Ground
Vcc = Positive


I hate to overcomplicate things.

But Skylined's post kind of oversimplifies things.

There are two main kinds of transistors, bipolar, and field effect.
Bipolar Junction Transistors (BJTs) have base, collector, and emitter terminals. Field Effect Transistors (FETs) have gate, source and drain terminals.

All these subscripted voltages are, are supply voltages at these terminals:
VCC collector
VEE emitter
VSS source
VDD drain
(base and gate are usually where you apply a signal, rather than a supply voltage.)

So far all this is general info.

Let's talk about logic circuits for a second, and we can include processors for purposes of this discussion. For logic circuits, it's a decent generalization to make that VEE and VSS are ground. And then VCC and VDD are positive voltages, the exact value of which depends on the type of transistor making up your IC, so check your datasheet. Usually there's a range given.

TTL logic ICs will tend to use the VCC/VEE, while CMOS will tend to use the VDD/VSS notation. ince ther are lots of TTL-compatible CMOS chips now (like the 74HCxx family exemplified by the chip used in that project), the datasheets have tended toward VCC/gnd, and that's what you'll see on a current 74HC374 datasheet from Philips.

Once you get out of logic circuits, it's not generally true to say that VEE or VSS means ground. They could easily be a negative suply to an amplifier circuit.

I hope that clears things up. But I rather expect it doesn't....
Skylined was right, but don't generalize what he said beyond logic circuits.
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PIYIRIO

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electronics problem involving pics, 64 leds and lots of hair
« Reply #6 on: September 17, 2004, 09:26:37 PM »

Quote from: linear
Quote from: Skylined
Vss = Ground
Vcc = Positive


I hate to overcomplicate things.

But Skylined's post kind of oversimplifies things.

There are... blah, blah, blah...

I hope that clears things up. But I rather expect it doesn't....
Skylined was right, but don't generalize what he said beyond logic circuits.


 :wtf: but vss is ground and vcc is positive...

but anyways... wtf does that thing do? are you going to blind the astronauts on the iss?
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bigal

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electronics problem involving pics, 64 leds and lots of hair
« Reply #7 on: September 18, 2004, 02:31:40 AM »

thanks for the help,
the circuit is soppost to make patterns, text and animations programed into the pic.

but when testing the LED block, i aplied 3 volt to all 64 leds...

F*****G BRIGHT!!!  8)  <- you need sunglasses!
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linear

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electronics problem involving pics, 64 leds and lots of hair
« Reply #8 on: September 18, 2004, 09:40:29 AM »

Quote from: PIYIRIO
:wtf: but vss is ground and vcc is positive...


My basic point, is that that's true for this circuit and others like it, but not in general. Skylined didn't originally qualify the statement, so I did.
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