12 LEDs with 3 I/O project

[heepofajeep]

This was a project that was a cutout from a magazine that peaked my interest, as it seems like a fairly straightforward project for a relatively new microcontroller hobbyist.

My questions come from the necessary parts, as seen in this schematic:
https://www.electro-tech-online.com/custompdfs/2007/01/6399101f1.pdf

Here is the list of parts, and my questions that follow:

1) 1N4148-- I was thinking of using **broken link removed** Digikey part.

2) BC182C This is what I am mainly unsure of-- what is this, and where do I get it? digikey didn't seem to pull up anything in stock that seemed like it applied..

3)BC213C Same thing as above?

4) The schematic states, "The decoupling capacitors are not shown."-- what are decoupling capacitors & where do I get them & how do I apply them?

Sorry for the very newbish questions, but your help is VERY much appreciated, and I would love to be able to accomplish this project. Here is the reference to the full project writeup: **broken link removed**

Thanks again!!!

 

[eng1]

1) 1N4148-- I was thinking of using **broken link removed** Digikey part.

?

2) BC182C This is what I am mainly unsure of-- what is this, and where do I get it? digikey didn't seem to pull up anything in stock that seemed like it applied..

3)BC213C Same thing as above?

These are general purpose transistors. The BC547B and the BC557B should be correct replacements.

4) The schematic states, "The decoupling capacitors are not shown."-- what are decoupling capacitors & where do I get them & how do I apply them?

You have to connect the decoupling capacitors between Vdd and Vss (as close as possible to the microcontroller). A 10 microfarads electrolytic capacitor and a 100 nF polyester capacitor connected in parallel should be fine. The elec. cap. is polarized and must be connected correctly.

 

[ericgibbs]

hi,
I have attached a modified dwg of your circuit, which includes some
information on the components you are asking about.

Is the PIC preprogrammed ?

Regards
EricG

 

[heepofajeep]

Wow, that was quick!!! Thank you guys VERY much-- that answered my questions perfectly.

Regarding the programming of the pic, I plan to do that myself, as that is part of what I want to learn. I have programmed a couple pics, so I don't forsee any troubles with this. The code is provided in the last link provided in my first post, so it *should* be pretty simple (cough cough).


**broken link removed** is the Ebay programmer I am using, which I have been quite happy with so far.

Thanks again for your help, and I will try & keep you guys updated on the project... it sounds very intriguing to me.

 

[heepofajeep]

Doh! I spoke too soon... I did run into a question with the pnp transistor...

How important is the collector current? Looking through digikey's product availability, it doesn't seem like there is one readily available that is 50V and 200mA... the closest I came was 50V 100mA. Here is the page I am looking at for Digikey's productshttp://catalog.digikey.com/scripts/partsearch.dll?FV=000102641e8c00193b800001&keywords=&mpart=&vendor=0&mnonly=0&newproducts=0&PV=421265444

Thanks again for the help!!!

 

[eng1]

Regarding the programming of the pic, I plan to do that myself, as that is part of what I want to learn. I have programmed a couple pics, so I don't forsee any troubles with this.

A couple of advices... the schematic refers to the SOT-23 version of the PIC10F200. If you're going to use the 8-DIP version, check the pin layout before building the circuit. Same thing when you program that PIC.

 

[ericgibbs]

hi,
the original transistor drawn was for Ic = 200mA, you can use a transistor
with a higher current rating say, 500mA without any changes.

The specs for the original transistors are available from www.datasheetarchive.com
if you want to cross reference them.

EricG

 

[eng1]

the original transistor drawn was for Ic = 200mA, you can use a transistor
with a higher current rating say, 500mA without any changes.

Yes, what about the PN2222/PN2907 pair?

 

[William At MyBlueRoom]

IMHO, the design appears to be demostrating a theroy not a practical solution.
Using a PIC (like a 12F) with only 1 more I/O pin would solve the problem simpler and cheaper than a 10F series using 2 transistors. The PICKIT1 uses this type of LED muxing and it supports 12 LEDs with 4 I/O pins.

When using PICs or any micro try to choose one with the I/O you need and avoid "glue" logic. That's why there are 100s of PICs to choose from, you can PIC & choose so to speak.

Take a look at my Firefly Assembly Manual. It's got code to use 3 I/O and 6 LEDs (or 3 BiColor LEDs)

 

[heepofajeep]

IMHO, the design appears to be demostrating a theory not a practical solution.

I agree, but since this is a learning experience for me theory is kind of what I am looking for... I don't fully understand the theory, which is why I am going to dive into this project & find out first hand (hopefully!)

 

[Nigel Goodwin]

I agree, but since this is a learning experience for me theory is kind of what I am looking for... I don't fully understand the theory, which is why I am going to dive into this project & find out first hand (hopefully!)

I would suggest you learn the basics first, once you have a reasonable understanding of those, then move on to more complicated things!.

Not only is this fairly hard to grasp, but because it's a dynamic function you can't easily even measure or test what's going on - you would need a multi-channel scope.

The entire idea is simply to show what can be done with a small PIC with a very small number of I/O pins, do careful programming and a 'sneaky' attitude