Topic: replacement for the Main ULA IC in the POD.

[Karl]

..... I don't expect any replacement pod to be too complicated, I'd just like to be able to produce something complete, something that you can grab, swap for your ULA (or pod board) and go.

Sounds just the job 

[aladds]

Right. I've finished Uni for the year, and although I do have a summer job I've got some time to actually put quite a bit of effort into this.

I've been looking at circuit diagrams, methods of checking battery level and current metering, and I think I've realised a few things.
Firstly, replacing the main ULA with a PIC is completely possible and shouldn't be too hard. I _might_ have a working prototype by the end of the week.
Secondly, it may be easier to make a whole new POD, Sinclair didn't use any Analogue to Digital Converters, so some of the inputs to the ULA aren't in ADC friendly form, I'll have to check that though. Hopefully I should be getting an old oscilloscope from our electronics lab today (if the lab techs are nice!) so I'll be able to properly analyse exactly what's going on in checking current & voltage. (Voltage is easy, current should be but the inputs to the ULA regarding current are confusing me)

The only difficulties I can see are, as I've said, getting the signals from the control box into a friendly form for analysis. Once that's done everything should be easy. Controlling the LEDs and buzzer, for example, is really easy!

Also, would anyone be interested in some sort of data logging? There's not that much information available, but I could get it to record current & voltage over time, for download to computer for analysis. Might be a little more work but shouldn't be too hard to do... That wouldn't be in the first version though!

[radiomarty]

Good stuff - Hope you can crack it !

[aladds]

Well our lab wouldn't give me an old oscilloscope (something about health and safety...) but I'll see what I can do without one. If anyone has one in or around Cambridge I'd be interested :-) (I might be able to make do with a PC sound card...)

[Karl]

Good luck with this mate, fingers crossed you get it sorted 

[aladds]

Well, currently having a little trouble working out what's up with my control box. It's good enough to drive but I think the 5v regulator is buggered up. I'm trying to work out exactly what's up and if i can swap a bit 7805 in for it. I've got one of those lying around so if I can that would be the best solution right now. My Pod is fully working as far as I can tell from running it on my desk, and I've started making a PIC adaptor for it. This will take a little longer than expected due to this 5v problem, but I recon I'll get something going soon enough :-)

[PLOD11]

I have replaced the 5 volt regulator for a 7805, and had no problems 

[radiomarty]

I have used this regulator on at least 3 repairs and as plod says no problems

[aladds]

Yep, just done it. Lights are now nice and bright but current sensing doesn't seem to work... Took it up the road later and it's still no good so I suspect the LM358 opamp... it looks ok, but someone might have previously released the magic smoke... I'll pop and get one tomorrow!
I've got to be careful what I do though, as I'm currently using it to commute to work, so I'd better not break anything!
As soon as current sensing works with the ULA I'll be able to start working out how I'm going to detect current with a PIC. I suspect it should be easy enough. Checking the battery level should be  a breeze. My little test board is coming along nicely, should be able to get some deliverable results soon.

[PLOD11]

Well done, keep up the good work ...

If you need a hand with anything let us know ....

PLOD

[radiomarty]

All good stuff mate - hoping you can crack it !

[aladds]

I've swapped a new LM358 in, but current sensing still isn't working, are there any other common issues the control box can have with current sensing? The wiring to the current shunt looks ok... Perhaps my ULA is shot (not necessarily a problem, but might make it a little harder to work out if my PIC is working properly!)

[aladds]

Update.

Ok, so this project has had a little bit of a setback due to unforeseen (unrelated) circumstances which have consumed much of my time. That's mostly sorted out now, although there are still a few things I need to do. Anyway, the important thing is I can now devote a little more time to making a new ULA. With luck I can show something off soon :-)

[Karl]

No worries mate , just pleased you're having a go at sorting it  .

How long it takes isn't really an issue 

[aladds]

I still need to fix my current sensing, it doesn't report anything at the moment, but I've made a little more progress. I've got a preliminary circuit diagram, some skeleton software code and a half-built hardware prototype. It's hard to find the time to work on this, but I should be able to finish off the hardware and start implementing and testing software in the next few weeks.

At that stage I'll only be able to display values, buzz the buzzer, read the voltage, report that everything is ok (or not!) to the control box and *I think* read the inner temperature probe. As my current meter doesn't work at the moment I won't be able to test that to see either how it works or try to guess at re-implementing it. Obviously if I get that working then I'll have a much better idea of how to set that up!

I'll keep everyone posted as to my progress, of course, so watch this space!