picaxe and 60 led's

W

wombweller

Member
Hi All

Can 60 individule LED's be flashed one after the other from a PICAXE chip.

I'm looking at putting a 1hz pulse through the chip so each LED will flash in 1hz steps.

Please advise me and help me get on the right track.

Cheers!! Mark
 
hippy

hippy

Ex-Staff (retired)
The answer is "yes". There's a number of ways to do it but if only one LED is to be on at a time you can do it with multiplexing or charlieplexing.

Any PICAXE with just 5 or 6 bi-directional I/O lines could control all 60 LED's ( I haven't got the brain power at the moment to work out the exact number ). I'd probably choose a 20X2 and it may be possible with a 14M and you could even do it with an 18X and some fancy software trickery.
 
W

wombweller

Member
Thanks a lot, this will give me a basis from which to start.

I will search through what is suggested.

Kind regards
Mark
 
E

eclectic

Moderator
Well, superficially, the SiChip clock
and the pocketwatch look similar.

You've now got a circuit and the programs
as a start. (See post #10 edit)

How's your PCB making and SMD soldering. :)

The best start?
A breadboard / Picaxe / LED's ............
e
 
W

wombweller

Member
eclectic said:
Well, superficially, the SiChip clock
and the pocketwatch look similar.

You've now got a circuit and the programs
as a start. (See post #10 edit)

How's your PCB making and SMD soldering. :)

The best start?
A breadboard / Picaxe / LED's ............
e
Click to expand...
Hi

Cheers!! done enough vero soldering to get me through this project.
Don't think I will be using SMD. components.

Are there any advantages/disadvantages with multiplex and charlieplex, what would suit this project best?

Cheers!!
 
E

eclectic

Moderator
wombweller said:
Hi

Cheers!! done enough vero soldering to get me through this project.
Don't think I will be using SMD. components.

Are there any advantages/disadvantages with multiplex and charlieplex, what would suit this project best?

Cheers!!
Click to expand...
I'll leave it to the experts to discuss MP vs CP.

Going back a few posts, how do you envisage the
"pendulum" as a timebase?

e
 
hippy

hippy

Ex-Staff (retired)
wombweller said:
Are there any advantages/disadvantages with multiplex and charlieplex, what would suit this project best?
Click to expand...
Not much difference in multiplexing or charlieplexing IMO; charlieplexing wins because it uses less I/O lines. No reason to use shift registers or external muxes if there's no need.

This isn't 'multiplexing' in the high refresh sense, just a matter of setting the right I/O to the right state every second. Should be quite straight forward.
 
W

wombweller

Member
eclectic said:
I'll leave it to the experts to discuss MP vs CP.

Going back a few posts, how do you envisage the
"pendulum" as a timebase?

e
Click to expand...
Use a 1 sec length pendulum and use this to trigger either by opto switch or transistor through electromag coil.Use the pendulums natural rate for the 1 sec pulse!! something along those lines anyway!!
 
W

wombweller

Member
papaof2 said:
How will you drive the pendulum? It must enough energy added to overcome friction.

John
Click to expand...
Hi

That's the easy part.Obviously there are a number of ways to give the pendulum an impulse/kick and surprisingly very little effort is required to keep the pendulum swinging.

1) hipp/toggle
With and hipp toggle arrangement and an electromagnet when the pendulum's arc falls to a low level the hipp/toggle gets triggered and makes connection for the electromagnet and this gives the pendulum a pull.
This is an age old solution.
http://www.youtube.com/watch?v=lmx5iy4qwhI
This method was used in many clocks including post office/telecommunications.

2) Electromagnet,magnet and transistor arrangement..
By taking advantage of the electromagnets ability to generate small amounts of electricity when a magnet passes over it.By attaching a small magnet to the end of the pendulum and placing the electro coil either at zero or just off we can amplify the small amount of electricity that's generated.This is amplified with transistor arrangement,We can do this with two coils where one coil senses and the other impulses on that sensing.This can also be achieved with one coil.

Again this method is used in many electric clocks and particularly the small mantle clock with rotating balls.

I am going to use method 2. as good results can come from this.You get a free swinging pendulum that is able to produce a very accurate 1 sec pulse via the amplified transistor circuits and with the addition of a PICAXE the worlds your oyster!!! very minimal friction...

Mark
 
hippy

hippy

Ex-Staff (retired)
If the LED's require more than 25mA each then a simple PICAXE-only multiplexing or charlieplexing scheme won't likely be sufficient. Some sort of anode / cathode drivers would probably handle higher currents and would be suitable for a multiplex scheme.

Most high-brightness LED's can put out significant light for just a few mA, so unless this is for a clock tower or using 'headlamp-style' LED's I wouldn't have thought requiring in excess of 25mA would be necessary. Only wombweller can actually tell us what is required though.
 
W

westaust55

Moderator
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W

wombweller

Member
W

wombweller

Member
hippy said:
If the LED's require more than 25mA each then a simple PICAXE-only multiplexing or charlieplexing scheme won't likely be sufficient. Some sort of anode / cathode drivers would probably handle higher currents and would be suitable for a multiplex scheme.

Most high-brightness LED's can put out significant light for just a few mA, so unless this is for a clock tower or using 'headlamp-style' LED's I wouldn't have thought requiring in excess of 25mA would be necessary. Only wombweller can actually tell us what is required though.
Click to expand...
For my clock project I will use mid range 5mm LED'S max 25mA. :cool:
Still not finalised project details yet.

First I need to know how to write the code in PICAXE including charlieplexing.

Cheers,
 
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