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Topic: Pitolino - a small data logging gadget (Read 12575 times) previous topic - next topic

pito

Aug 01, 2012, 10:13 pm Last Edit: May 01, 2014, 07:40 pm by pito Reason: 1
Hi, I could not resist the temptation to design something small and maybe useful  :)
Pitolino:
1. v2 49.53x49.53mm, both sides smt parts 0805, etc.
- 4 mounting holes for M2 (holes 2.2mm diam.)
- Sanguino pin numbering (avr_developers variant)
2. atmega1284p smt, 6pin programming header
3. uSDcard socket with P_MOS SD_VCC switch and olimex-like card det.
4. PCF8563T, low power RTC, 200nA current, with opt. alarm to PC7
5. USB mini connector - as 5V power supp. only, optional
6. MCP1700 3V3 low drop, 1.6uA v-reg
7. battery holder - CR1216, 10y with above RTC
8. serial header - with sparkfun-like pinout and opt. cap in DTR for reset
9. all atmega pins put on headers - 1500mil header's rows span fits
the larger solderless breadboards (spans over 2 boards), headers with 0.1" pitch
Any feedback welcomed..  :)
p.

Constantin

Two sided board? Where is the RTC that presumably the crystal and coin cell are for?

Should be fun to assemble.  :)

pito

#2
Aug 01, 2012, 11:18 pm Last Edit: Aug 01, 2012, 11:35 pm by pito Reason: 1
RTC is on the bottom side - see the blue picture - placed near the battery and 32kHz resonator...
PS: the board is 49x42mm (!!) - not easy to pack all the stuff on the top side only when using 0805 :)
PS1: that is the old_school design - tubes on the top of the chassis and caps, chokes, resistors on the bottom side :)

florinc

Cool.
It would be nice to see some mounting holes as well. I find them useful lately.
Price for the PCB in the same range as the small bobuino?

pito

#4
Aug 01, 2012, 11:51 pm Last Edit: Aug 01, 2012, 11:57 pm by pito Reason: 1
Mounting holes - hmm, difficult with this breadboard concept, the board is quite small..
PCB price - itead will tell me :) (it fits in the cheapest range)..

florinc

It would be also nice to have provisions for another RTC chip, and I am thinking DS3231.

pito

PCF8563T is $0.80 and 200nA, DS3231 is $8 and 800nA (but 2ppm - nice)..

florinc

I like it.
Shouldn't the coin battery have an exposed pad for the negative terminal?

pito

#8
Aug 02, 2012, 12:20 am Last Edit: Aug 02, 2012, 12:35 am by pito Reason: 1
The exposed pad is there - on the top side - at least I can see it with gerbview..

CrossRoads

Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

pito

#10
Aug 02, 2012, 11:17 am Last Edit: Aug 02, 2012, 12:08 pm by pito Reason: 1
Added 4 mounting holes, 49x48mm size now, and numbering scheme as per avr-developers.
A lot of opened Qs. See the first message.
p.

Constantin

Good stuff but again, why the two sided design? Dual-sided SMD assembly is a pain as far as I know... I restrict my boards to through-hole components on one side and SMDs on the other. But that's because I'm lazy and use stencils + a reflow oven to attach my SMDs to the PCB.

Also, I choose my board sizes to coincide with mounting holes inside Serpac or Hammond plastic enclosures. Just a thought.

pito

My goal is to have the pcb small (max 49x49mm) such it fits to Itead lowest pricing. And also low power. No special enclosure in mind. Soldering - a few resistors, caps, choke, and diodes are ~0805 which is doable manually without a stencil, the chips are easy to solder, I think, too.
So - a quick solution if somebody wants to log some data into a uSDcard at a remote location.. Maybe 2.7Volt VCC would be enough and you can use a 3.7V lion or something like that. I am also thinking to replace the 1284p with 328p as it seems to me the 1284p is an overkill here..

jraskell


I am also thinking to replace the 1284p with 328p as it seems to me the 1284p is an overkill here..


328p or 324p?

BlueJakester

#14
Aug 03, 2012, 04:33 pm Last Edit: Aug 03, 2012, 04:34 pm by BlueJakester Reason: 1
When working with a board like the Pitolino Shield pictured above, how do you go about connecting the pins of parts? Solder wires to the pins or some sort of J connector?

As a beginner, all of the solder boards I've worked with so far have connected rails/traces.

Thanks,
Jake

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