Martin's ATtiny85 pulser boards on eBay

[Martin]

I just put the first batch of ten up for sale on eBay. I'm charging ten pounds each with free delivery to the UK, and an extra £2.50 for international delivery - but let me know if you want more than one, as the boards are tiny and light so I can absorb the postage costs for multiple sales.

According to eBay, when I listed the item, if you use this link instead of searching on eBay, it reduces the charges I have to pay, somehow,

ebay listing

Let me know if you spot any mistakes in the listing. I'm not used to listing multiple items so I might well have cocked it up - I think there's a way for me to edit the listing if necessary

I don't know if the listing runs out in seven days even if all the items haven't sold, or if I have to relist them or whatever. You can always drop me a Private message here if eBay isn't working out.

I'm hoping to keep this thread fairly uncluttered so that people can find the information they need easily. Please post in the other thread for general comments.

Click image for larger view.

[ChrisBe]

Hey Martin. Had a chance to try one of the ATtiny85 pulser boards with an old Adams 2R-HV and an even older Southwestern RC magnetic actuators. I like the results. Hope you be make another batch of boards. Thank for giving me a fun project to work with. Cheers! Chris

[Martin]

Prompted by Spike, I checked my stock of completed boards, blank PCBs and components on hand, and the availability and cost of new parts. I'll have about thirty of these boards tested and ready for sale early next week. I'll be charging £12.50 each plus post and packing this time. I've not listed them on eBay yet.

I have enough PCBs to make another forty (seventy in total) but the TB6612FNG H-bridge driver chips seem to have been hit by the global chip shortage and are listed on Mouser as not available until October! I found someone selling these chips (probably clones) in China for about £5 each, including postage!

This post is really to find how many people, especially those in countries other than the UK, are interested in buying one/some. I could maybe ship a bunch of them to someone who could act as the local dealer to save on international shipping/customs duty costs. Obviously, even in the UK, there are some shipping costs to be saved if you want to share a delivery with one or more local friends.

If I end up going to Ponte (I'm planning to attend) then I can bring some there too, unless they've already sold out!

[Spike S]

Thanks, Martin.
Quite happy to act as your Southern (UK) agent to make just one P&P package. Total of five currently known; three for me and two for Twitcher please.
£12.50 per board is still a bargain !
Post here if you wish direct dealing or from Ebay when you get to that point. Presumably if direct from you, you prefer Paypal payment ?

Personally I would not wish to wait until Ponty. Not sure if conditions will allow my attendance, no matter how much I would wish to be there.

[Martin]

I assume you want all those five in the normal 'finished' state with the connectors soldered in place and the heat shrink tubing applied? I should be able to finish testing them tomorrow, and can post them to you on Wednesday.

[Spike S]

PM sent

[Martin]

Sorry Spike, they're all built, programmed, calibrated, but failing on test. A couple work okay, but even those aren't 100% reliable; the others either don't run at all, or only drive in one direction.

I'm still investigating. The communication with the ATtiny works, so the H-bridge drivers are the suspect parts. I've no idea at the moment while they're all bad - maybe I left them in the ultrasonic cleaning bath too long?

No chance of sending them now today, I'll update you on progress if and when I make any!

[Spike S]

The occasional (?) frustration of those Electronic Gremlins !
Nil Illegitimae carborundum.
Don't panic.
Spike

[Martin]

I've spent the last few days trying to track down the faults. Here's what I've done on each board of a batch of six:

• Reflowed the solder and cleaned the board again - made no difference.
• Unsoldered the H-bridge chip, cleaned underneath, resoldered in place - made no difference.
• Reflashed the bootloader, recompiled and uploaded code, reclalibrated OSCCAL - made no difference.
• Wondered if an update to the Arduino IDE was somehow causing a bug, so got the one working unit and did the bootloader, upload, recalibration to that too - it still worked perfectly afterwards, so it's not that.
• Used the AVRdude program to check the settings of the ATtiny85 'fuses' (internal settings, some of which the Arduino IDE doesn't change). All the same as the one working unit.
• Removed the H-bridge chip, fitted brand new one, cleaned, belled out every track on the board to test for shorts - made no difference.
• Fitted extra decoupling capacitors - made no difference.
• Measured the total decoupling capacitance of each board - all similar and all the same as the working board, to within normal capacitor tolerances.
• Tied ATtiny RST line high (on the board it's pulled up by a resistor) - made no difference.

The fault is that the pulser works correctly for low-power pulsing, but as the 'aux' channel is increased for more power, the motor suddenly switches to just run in one direction. If the 'aux' channel is reduced, the motor continues to run. Resetting the ATtiny, by momentarily shorting RST to GND corrects the problem until the next time 'aux' is increased beyond some (low) threshold. The one working unit, an older one, which is apparently identical in all respects, works fine up to 100% AUX input with the same power supply, pulser motor, receiver and transmitter.

It appears that load on the motor and H-bridge somehow causes the ATtiny to hang, but I've no idea why and can't think of anything else to try.

If it were a fresh batch of chips, I'd think I'd bought some fake ones (either the ATtiny85, not that I've come across fakes of those) or the H-bridge. But I'm 99% sure that the chips were left over from building the previous (all working) batches of boards a few years ago - and they've lived in their anti-static packaging in room temperature storage ever since.

So I'm going to have to give up on these boards, unless someone can think of something else to try. Sorry Spike. I've spent most of my spare time for the last week building and fault-finding these damn things, and I'm now completely out of ideas.

[Spike S]

Martin
How frustrating, I know how debugging can be so time-consuming. Thanks for that report and all your efforts but do move on - it's only a hobby.
I will continue in true Mode Zero, button flying, for now as my ERK is a delight flying in that mode.
Perhaps one other of the software Gurus on this site might be able to suggest a solution idc, if only to answer the many question that will have been swimming around your head !

Anyone who says that Grammar and Speeling (!) are not important has never tried writing code. I have only recently found and corrected a bug in 4-year old Pickaxe Basic code for one of my Sailability contacts. It's amazing what quirks a misplaced line return can cause.

Spike