Building a circuit with an 08 chip

abenn

Senior Member
I've been using the 08 protoboard for some time now to experiment with sound and light circuits. I now want to make a module to install my circuit into an RC model aircraft, probably using Veroboard or similar.

Just two questions really:

1. Do I simply build my circuit -- replicating the circuit I've built on the protoboard -- using an 08 processor into which I've already downloaded my program while it was in the protoboard?
2. Do I need the 10k and 22k resistors which the manual says "must be included for reliable operation". Or are they only needed when you're downloading a program?
 

craig008

New Member
yes youo do need the download circuit for stable operation of the picaxe, also handy foir making programme changes and fault finding.

as for circuit constructioni start by maiking the "bare bone" circuit and check that it donwloads, and then add in the next bit of circuit and see if that works. other than that the circuit can be identicle to that of the prototype
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Hero Honda Hunk History
 
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BeanieBots

Moderator
No, you don't need the download circuit.
What you must do, is make sure the serin line is held low. An easy way to do that is with the download circuit so for the sake of a few resistors, you may as well include it.
Using header pins takes up very little board space and a servo lead can be used for connecting which then gives the advantage of in-circuit programming.
 

WHITEKNUCKLES

New Member
If you would care to look at my thread describing the 'sideboard' and think that one of these bare boards might help I could send you an earlier version to practice on.

Dave
 

manuka

Senior Member
IMHO all PICAXE circuits should allow for in situ programming. As BB says, a couple of resistors & a discrete 3 pin socket mean you'll be laughing when program tweaking arises. And it WILL! Never mind Vero board- we've taken to using a slick & cheap fi-glass NZ designed "Kiwi Board" for soldered versions- these include provision for a 7805 & program socket(& the 10k/22k)
 

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moxhamj

New Member
Re the two questions - 1) you can simply rebuild the circuit and 2) the 22k/10k are not needed if you tie physical leg 2 to ground. I started off building in-situ programming boards with download sockets but more recently I started experimenting with removing non-essential components. My preferred technique now is to program the chip on a protoboard and then move it to an 8 pin socket on the final board. An IC insertion tool is very handy (worth a few dollars). The main reason I do this is many of the picaxe circuits are hard wired into various locations and removing the whole board/box/cabinet is difficult. Moving the computer to the circuit is also difficult. Much easier to remove the chip, reprogram it and pop it back again. I am finding most chips do not need reprogramming (I have over 30 picaxe chips controlling things round the home). I think this depends on the final application - if the picaxe is acting as a sprinkler controller it is unlikely to need changing, but if it is part of a robot it may need to be tweaked endlessly.
I would always use an 8 pin socket - tempting as it is to save a dollar by soldering the chip in place this will be the one chip that decides to die for no particular reason.
Manuka's board looks great and because it uses the same layout as a protoboard it makes it very easy to transfer the circuit over. Are these available commercially?
 
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Wrenow

Senior Member
Abenn,

You might want to consider using the AXE024 board. It is very small, reasonably priced, and has some power conditioning that you might find beneficial. And the download circuit. You can you can also use the servo outs as inputs where appropriate - the 330R resistors do not bother the RC pulse.

And, you have ready access to the other pins through the colour sensor provisions.

Using this board really helped stabilize my project.

Makes for a nice, neat, small final project.

Cheers,

Wreno
 

abenn

Senior Member
Thanks to everyone who's responded :)

I propose to use a socket for the 08 chip, mainly because I don't trust myself to solder one directly to the board without damaging it. But that means I can remove the chip if it ever needs reprogramming, so I think I'll do without the input circuit.

I understand the bit about tying physical leg 2 to ground; but can it be a direct link, or does it have to be a 22k resistor like in the manual?

I've drawn a layout of my circuit using a piece of veroboard, and it's such a simple one that it's not worth me buying -- or even making -- a more-elegant printed circuit, but thanks for the references :)
 

manuka

Senior Member
"Kiwi Board" only available in NZ at this stage, even though PCBs made in China. I put input into it ( predictably!) but am not the distributor. If enough folks put up their hands I'll pass interest on for wider promotion & availability.
 

hippy

Technical Support
Staff member
I understand the bit about tying physical leg 2 to ground; but can it be a direct link, or does it have to be a 22k resistor like in the manual?
The simple answer is you can connect Leg 2 direct to 0V. I have, others have, and there's been no ill effects seen.

The longer answer; it would be good engineering practice to never connect the leg of any IC which could become an output to 0V directly and a resistor should be used. Under fault conditions Leg 2 could become an output but that's not likely to happen. How likely is the question for which there is no definitive answer. Minimal risk I would say but don't expect a definition of minimal :)

If you are prepared to accept that a fault condition could result in damage to the PICAXE then you can use a direct to 0V connection. It's a low enough risk which most hobbyists would be prepared to accept.

If you choose to use a resistor it only has to protect the pin / port from excessive current draw so any convenient value you have between 1K and 47K is usable, and in reality the range could be even larger.
 

abenn

Senior Member
Thanks hippy. Using a resistor is no problem -- especially as I need to link two tracks on my veroboard -- so I might as well follow "best industry practice" :)
 

abenn

Senior Member
Successful outcome

Thanks everyone for the advice and confidence-building :) I've now built my circuit on a piece of veroboard and, apart from initially missing one link between tracks, it works.

I omitted the input circuit, used a 22k resistor to connect leg 2 to ground, and used a socket for the chip. Maybe not a big deal for you gurus, but for someone who hasn't built anything electronic since 1982, if nothing else it's given me confidence that I can handle these tiny components (four output transistors soldered close to the board) without instantly frying them ;)
 

hippy

Technical Support
Staff member
Well done and congratulations; welcome back to circuit construction. I particularly liked your thinking on dealing with leg 2; I need a link wire so may as well use a resistor.
 
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