Clock kit Part 2

With the schematic in hand I was itching to get my solder on.  The board itself appears to be somewhat generic, in that not all components labelled on the board need to be fit for this clock to be complete.  Using the schematic and the parts received list we were able to figure out what needed to go where.

Before I go through what goes where, a general note is that I soldered all of the SMD components on the back of the board, starting in the middle working my way out.  Then all of the SMD components on the front.  And then the large components on both sides as it made sense.

As mentioned, the board is two sided.  The back of the board is the tricky one of the two.  All of the big components are labelled clearly and so are straight forward.  The only exception is the power supply components - which can go at either end of the PCB, it's completely up to what suits you.  The SMD components needed to be worked out using the schematics and then a meter to see what pins/pads matched.

The following were soldered onto the back of the board:

• C1   - 10μF
• C2   - 30pF
• C3   - 30pF
• C11 - 0.1μF
• C12 - 30pF
• C14 - 0.1μF
• C15 - 10μF
• C26 - 0.1μF
• R1   - 10kΩ
• R2   - 10kΩ
• R3   - 10kΩ
• R4   - 10kΩ
• R6   - 1kΩ
• R11 (or R12 or R13) LED - 270Ω- can choose 1 of these 3 - just need to match it below
• Q1   - Transistor
• BT   - Battery
• U1   - STC12C5620AD
• U2   - LPD6803
• U3   - DS3231
• Y     - Crystal
• Bell
• T1 (or T2) - Temp Sensor (using 3 wire ribbon cable to extend)

Power supply bits (I chose the right side looking at the back of the clock):

• C16 - 0.1μF
• C19 - 100μF
• C21 - 100μF
• C22 - 100μF
• R7   - 4.7kΩ
• USB header

On the front of the board (the side with the display) everything is pretty much as labelled.  All resistors need to be fitted and are all 10k.  All capacitors also need to be fitted and are all 0.1micro caps.  The IR receiver  goes where marked.  All IC's under the display blocks need to go on.  The display segments are fitted with the decimal point at the bottom (the bottom matching the text layout on the board).  The LED's that act as separators will need to use the common labelled pin and the pin matching the R11/R12/R13 on the back that you chose while doing the back of the board previously(just use a meter to check).  There's also a 4 pin programming header - which I'll get to in a minute.

While soldering the display blocks in I powered it up to check each one, and they were working - but displaying some weird characters.  All segments of the display blocks did work though so I cracked on and soldered all 6 display blocks.

Once complete, I plugged it in and got this:

It took a minute to realise the display was inverted.  Instead of turning on the segments to display a digit, it was turning on the inverse segments.  So the above should read 00:02:09

This was again a point I had to "phone a friend".  After desoldering a display block and flipping it to no avail, we went digging through the documentation we had.  BINGO!  The VFD clock that this clock is based off has different drivers for the tubes - which invert the signal they receive!  This hadn't been taken into account in the source code I was sent by the seller (it had just been used as is by the looks of it), and so instead of setting the bits to turn on - its actually setting the bits that should be turned off for each digit.

Realising that the STC12C5620AD would need to be flashed with new code at least meant that the clock was physically put together correctly.  I've started getting setup to program the STC12C5620AD with new code - that will be covered in Part 3.

Clock kit Part 1

So I decided I wanted to some sort of small digital desk clock to build.  After looking around people seemed very impressed with clocks using the DS3231 chip, so I googled around for clock kits using that chip and came across this kit from Ali Express.

Looking pretty cool, being about the right size with the right chips and with some SMD components for me to practice soldering I ordered one and went to sit by the mail box.

The kit did take several weeks to show up - but this was over Christmas - so i'm not sure if it was slow shipping or just that time of year.

The kit itself arrived well packed but appeared to be missing one thing.  There were no build instructions or documentation anywhere to be found.  I emailed the seller thinking maybe they just don't bother printing them and would just email them through.  There was a bit of a language barrier with the seller, but after a few emails he sent me some zip files.

Opening these up it appeared like he'd zipped up the documentation for a world of electronic kits.  Schematics, code, data sheets - all sorts of stuff.  I had a good look through everything I had, but could see anything that matched exactly the kit I had in my hot little hands.  I did notice some logos/urls for other blogs and shops online selling other kits - but I couldn't find any blog posts or kits matching the one I bought.

In steps my good mate to the rescue!  I sent him the zip files and he had a look through them.  Through a bit of detective work (and a huge amount of experience) he came to the conclusion that the design for the kit I had was based off this VFD clock (you'll need google translate).

With that in mind I packed up the kit and headed over to his place to have a crack at putting the kit together the below schematic as a guide:

In the Beginning...

So I'm the type that has alway dabbled in electronics - but I don't do it for a living.  Thankfully one of my best mates is a seasoned engineer, and is always willing to give me a hand or answer any questions I have.  This blog is just intended as a place for me to write down some notes as I build/learn what the hell I'm doing.

The first series of posts are going to be about me building a small clock kit that I recently purchased, and the ongoing experiences of getting it working.