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Respite Randomness

A project log for DECAL

Decal Evolved-Composite Application Layer for robotics

morningstarMorning.Star 07/27/2017 at 09:402 Comments

I've been on a few days Respite. While Bea goes off to spend time with her mates and have a laugh, I kick back and chill out. Plus I'm not bothered about the competition now and have de-stressed considerably. I should not have entered in the first place; it put pressure on me I dont need and to be honest winning anything significant is pointless really.

I could buy my house I suppose, then I can run a business out of it.

But a residency I couldnt use would cause me pain, and little cash prizes only prolong my suffering; the reality is I'm just fucking about with servos and scrap. More servos and scrap aint going to change that, and I cant even teach, let alone manufacture or supply anything in a poxy little council maisonette. All I get to keep of anything I earn unless I work full-time and get off benefits, is 20 quid in a week.

Would you give the government 90% of the commission on one of your paintings? Doubt it, even if you didnt want to flaunt working for more than 16 hours in a week to produce one. Honestly, the only reason I do anything is because I get suicidally bored sat on my arse waiting for Bea to snap her fingers otherwise.


Anyway...

I managed to do a bit of research on a missing component I needed to make reliable flex circuits. I have some etch resist I bought as a kit. It worked great, but the developer and literature for it vanished during the move and I hadnt seen either since. Still didnt have developer, but at least I know what it is now.

NaOH... Hmm, sounds familiar, Sodium Hydroxide...

Probably the last of this I'll be able to buy over the counter, thanks to the morons who will use whatever is to hand to hurt others as well as their own stupid selves. I'll be careful with it, like I would the sulphuric and hydrochloric acids I can no longer obtain. As it is I'm reduced to metal-salt etch because the alternative is Ferric Chloride, which is nasty, hard to dispose of, costs a fortune and is only available mail order. I have Bicarb and Copper Sulphate though, both are better than table salt. About a table-spoon of this per litre of water should do it, and I can just pour it down the drain the same as the etching solution.


I had a spot of bother with the communications in the processor board. It seems the CP2102 is setup to drive the 5v Atmels at 3.3v level, which works ok. That means I shouldnt need a level shifter so the ESP module can talk to them over serial. I will need one to step down the voltage when the Atmel talks back though.
So I've added a 3.3v Zener and some current limiting resistance between them. This is in programming mode, the 6.8ohms dont affect the USART, and the Zener just blocks the Tx voltage from ground as it should. In run mode the ESP Rx is driven by the 5v Atmel Tx, however this drives the Zener into breakdown and it bleeds off the excess voltage to ground.


Sneaky

While messing around pulling chips and scratching my head over these issues I discovered a great method of pulling multipoint SMD devices off a board again, useful for repairs and harvesting alike.

Because I only had one 117 regulator handy and suspected the chips for the faults, I wound up moving it about a bit and they arent easy to desolder without a hot-gun or oven.

Adding an ESP makes that completely impossible. I've ruined more than one PHH device trying to harvest it or work with it because those edge connectors are delicate at best. They were never designed to be desoldered in the first place...


Using just a fine-tipped iron and a piece of Kapton tape folded in two so it isnt sticky, I heated the pads one by one and slipped the tape between the device and board to break the solder without lifting the device and straining the PHH pads. It works cleanly and simply. :-)

I also tried the silicone-paper backing from the metal tapes, which works but not as well because it's thicker and frays. And regular paper is also a little thick, frays, and drags the solder everywhere but also works in a pinch.


Just Garbage

I've had a chance to cool down and not just blame my tools like a bad workman.
I have barely used these since I bought them, one had a ZIF socket because I used it as a programmer for raw chips, and it was more often than not tied to the other one for flashing.

Strike 1
Despite this, one of the Uno's has a dead 117 regulator, so when I jumpered the ADC to 0v, 3.3v and 5v, I got a reading of 0 instead of 640 in between the 0 and 1023 I expected to see. I only discovered this when I tested it with a multimeter. I didnt suspect it was broken, because the other one behaved the same.

Strike 2
That one has a broken trace somewhere and the ADC doesnt work on that one either. The 117 is ok on it though. Being 5v Arduinos, the digital ports work just fine.

Steeerike 3, you're outta here
The FTDI chip in the Mega2560 has failed completely. It isnt bricked; I cant recover it by reflashing if the USB port cant even see it, but I can still use the 2560 via a USART and power it from USB. The ADC works perfectly, throwing me into confusion as the chip isnt swappable.

Stinking up the place
Just to add insult to injury, I upgraded the IDE so I could program the ESP with it, the old version doesnt support the binaries. Bad move, Arduino have added a Serial Plotter, like the rest of the IDE its written in Java via Processing. Most people, granted, only have one monitor and would never find out you cant run Inkscape and Plotter side by side. It does something nasty to the display, PrintScreen cant capture it and clicking on Inkscape just segfaults it all the time Plotter running. I lost hours of foot templates I had minimised and forgot to save before testing the comms, and it only blew up when I maximised it.

And that, my friends, was responsible for me not putting a walking robot in the competition. My motherboard, had I been brave enough to parallel-test the sensors and it together, works perfectly. It was faulty genuine Arduino boards responsible for the chips not working all along.

Bad workman my arse, serves me right for not buying cheap knockoffs and expecting trouble.

Discussions

Dr. Cockroach wrote 07/27/2017 at 11:21 point

Just glad you have de-stressed :-) And I thought that tracing my issues was tough ;-)

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Morning.Star wrote 07/27/2017 at 21:17 point

Stress is one thing, it actually takes my mind off the underlying theme that I shouldnt even be doing any of it, not like this... Its a physical lump in my throat. I've been hearing muttering about justice around me, no-one actually says anything and I could just be sensitive to it, but there it is... Pointless trying to humiliate our toady administration, though, they know what they are.

I hope I havent kicked Aaaarghduino too hard, its not like theyre new boards but I did expect better than 100% failure, or I'd have just blamed the chips and given up when all five didnt work in either Uno. Sometimes you have to hit every knuckle to prove theres something wrong with the hammer, lol.

You say that, but when I think of the metres of wire you've soldered by now... If you'd soldered something in the wrong place, I'd never find it :-)

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