where to start

[MrScaussie]

Ok, long time lurker finally taking the plunge.
Dabbled with 08M doing nothing more that switching a relay on and off with only a few lines of code. It worked as required so never bothered going any further.
Decided it was time to put in some effort and learn to do something more useful than I have in the past. Downloaded the manuals and printed and bound them, downloaded the vsm software and purchased a licence. Bought various picaxes from the 08's through to the 40x which arrived yesterday. Already have the 7 segment displays, 74HC595's 74HC165's and 24LC16B eeproms.

Basically I am going to (try) to learn how to add three 7 segment displays, write some code to count from 1 to 100 and display the output on the displays.
So I have spent this evening reading through various threads, looking at the demo files in the VSM program and getting myself confused as to where to start.
I thought the whole idea of the software was to 'build' a circuit test it and write some software, then when it worked finally build it.

Of course looking in the libraries of the software didn't help as there a 100's of parts, how do you choose which parts to use where?

Since I have a range of picaxe chips I'm not to bothered if I use a chip that has too many i/o's I figure once I build something useful, I can also downgrade to a smaller version chip if I don't use all the i/o's or vice versa.

So I guess I'll be asking lots of questions along the way.

 

[hippy]

Welcome to the PICAXE.

You're right it can be confusing when first starting and faced with what feels like an infinite number of choices. Once you have found your footing you will feel much more comfortable. The best way to achieve that is to start simple then build up from there; a simple LED flasher, as simple piezo beeper, a LED which lights when a button is pushed and so on.

Assuming you start with a LED flasher, Manual 3 will show how to connect a LED and Manual 2 describes the commands needed ( High, Pause, Low, Pause repeated ). I would personally suggest writing the Basic program ( or convert a flowchart ), running the Programming Editor Simulator, building the hardware on breadboard to see it work, then move to the VSM with that mini-project.

 

[BeanieBots]

You start by thinking through your problem in logical steps.
VSM will not SOLVE any design issues for you. What is does do, is give you information about what YOU have designed.

So let's take your task of displaying a number from 0 to 100 on three seven segment displays.
Software wise that's simple enough. Make a loop which counts from 0 to 100 and in that loop call a subroutine "Display" to show it on the LEDs.
Let's leave the subroutine for now because we don't know what the hardware is.

The hardware. 3 digits with 7 segments is 21 LEDs. I actually think a 40X has enough outputs to do that. However, does seem a waste of output pins doesn't it.
You could mutiplex the display using just 7 outputs for the LEDs and one output for each display. That would need 10 outputs total.
Suppose you wanted to do it with an 08M. Not enough outputs??
Then you would need to use some other chips to help.

This could go on for ever so I'll wait for some more specific questions.

 

[boriz]

1 Picaxe 18 (Subtype is not important, but X is better for future I2C projects)
1 Breadboard
1 Regulated 5v supply
1 Download lead
1 4511 BCD-to-7 SEG decoder driver.
7 330R resistors.
3 1k resistors.
3 Medium power general purpose NPN transistors. (Common cathode display)

Should be all you need.

P.S.
Some info about the 4511

 

[Michael 2727]

BB said you can't multiplex 3 x 7-segments with an 08M, that is true.
But you can use a 4026 based display driver with only 2 pins, one or two digits
work very fast, 3 to 4 digits can be a little slower as the display is refreshed
using N x pulses (number of individual pulses) and a reset pin.
Read - Picaxe_manual3.pdf - Output Device 10 - Seven Segment Display, page 20.

There is usually more than one way to do something, so find all the options then
make a decision which offers the best solution for you, be it cost, simplicity, size etc.

Welcome to the Forum.

 

[MrScaussie]

Thanks for all the replies.
I remember reading somewhere about 7 segment displays, which is why I started with this topic.
I couldn't find where I had originally read about it.
Well today I remembered where, it was in a book I purchased a while back which is fantastic.
It's called experiments in Mechatronics using Picaxe controllers, by David Lincoln.
One project shows you how to connect three 7 segment displays together using an 08 chip, even adding a pot to display the value of the pot.

So i guess I'll start with that.