Story of earth - this is just a story. - Page 1
Forum section: electronics / general

author: dan3460
author_rank: Frequent Contributor
timestamp: February 05, 2017, 01:34:53 pm
content: I have been working on this project for more than a month, previously I have worked with the Arduino environment and for this project I moved to Atmel Studio. Needless to say were many things I was learning at the same time.The project started with one breadboard, installed the MCU made the connections to be able to download the program, I verified that things worked before adding more parts. Coding is much better and organized under Atmel, something that I like, the only problem is that is hard to know what is going on in the chip, I probably buy Atmel ICE for the next project. Anyway back to my story.The project grew to 2 breadboards and other things strung around the bench. Connector wires all over, crisscrossing the boards. Started to have problems with excessive drop voltage between the two boards, added more wires to join the positives and negatives. Then the measurements of the sensors started to fluctuate and was becoming much harder to know if any problem was due to the sensor or to the code. So here is prototype #2, made on a proto board (I think that is the name).I installed a couple of sockets for the MCU and ancillary chips, joining them with soldered wires, installed the 5V regulator and power the board. No smoke, very small curren draw, good sign!. Install the MCU and chips, again no smoke and a "normal" draw, but nothing happened, nothing on the display, no clicks on the relays. Turned the board upside down, started inspecting all the connections and I realized that I have forgotten to put the 5V wire to the MCU.Turned the board on again and I got all kind of weird things, LEDs that were supposed to be off were on or partially on. The display would print some of the characters and flash or stop altogether. I was sure that I have made a mistake on wiring the board, that I had miscounted the pin order on the different chips on the board. After several hours of looking, testing voltages, taking long walks, the problem was revealed; I had forgotten to put the ground wire to the CPU. After wiring ground everything was back to life.I continued writing code and adding more of the peripherals of the circuitry, then after I added a tiny speaker for sound feedback, it happen again. The unit would reset when the rotary encoder was moved left or right, even when the part of the code did not check for movement on the encoder. I unsoldered the speaker, the last thing added, no change. Here we go again, checking voltages, ok. Checking code, ok. Maybe the encoder fail, disconnected one of the wires, worked fine. Then as I was counting pins at the underside of the board to reattach the encoder I saw it, I had a cold solder on the ground wire that I had installed a week ago, the MCU was sourcing ground via the encoder.The moral of the story is, when confronted with hardware problems check and recheck that connections, Vcc, Vcc- and ground are solid before moving to any other thing.Cheers.

author: switchedmodepsu
author_rank: Regular Contributor
timestamp: February 06, 2017, 04:05:29 pm
content: Please learn how to format text properly and create paragraphs.

author: Monkeh
author_rank: Super Contributor
timestamp: February 06, 2017, 04:28:16 pm
content: Quote from: switchedmodepowersupply on February 06, 2017, 04:05:29 pmSays the guy with the layout-breaking username.

author: dan3460
author_rank: Frequent Contributor
timestamp: February 07, 2017, 12:41:43 pm
content: Quote from: switchedmodepsu on February 06, 2017, 04:05:29 pmSure, what don't you teach me? As you know how to spell "properly" and "paragraphs", those are big words.

author: electr_peter
author_rank: Unknown
timestamp: February 07, 2017, 09:30:19 pm
content: Interesting story. It seems you have had 3 same problems in a row, unlucky. Did you check for the same symptoms and solutions after 2nd and 3rd problems appeared? Or was it full check from top to bottom?From this I take thata) VCC/GND/power rails/intermediate power rails/etc. should very high priority check list (current as well, if possible) andb) test components separately first and then retest semi-assembled system after each new component is added.

author: dan3460
author_rank: Frequent Contributor
timestamp: February 08, 2017, 01:09:09 pm
content: I guess the main problem is lack of discipline. When I moved from the airwires to the solder board, I was in the middle of creating code I was eager to get the functioning of the unit and start bench testing the project. So, I rushed to get things working and skipped the basic checklist, and the problems resembled either errors in the code or a miss wire but never occurred to me that the miss wire was ground.I fund a problem since then that testing revealed, I have been using regular opamps that produce outputs at about 1V under and over the power rails, which at 5V is too narrow. I just got some rail to rail opamps, so I have to rip out and reinstall, this for sure will create some problems.Thanks for the comment.