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 Chronodot Problems
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By: Anonymous: Steve () on Wednesday, December 30 2009 @ 11:43 PM PST (Read 5358 times)  
Anonymous: Steve

It appears that my Chronodot is not being recognized.

My clock works correctly without the Chronodot.

When the Chronodot is installed, one of three things happens:
1) The clock boots up in a couple of seconds, time set to 12:00 and blinking - just as it does with no Chronodot.
2) The clock does not boot up at all. No lights, no response to buttons, nothing.
3) The clock does not boot up for a while, then a light zips part-ways around one of the 30-LED rings, goes out, and then the clock lights up with the time set to 12:00 and blinking - just as it does with no Chronodot.

According to the manual, when a Chronodot is installed, the clock will start up with a time other than 12:00 and without blinking. This is not happening.

When the Chronodot is installed, is the clock supposed to remember the time between powering down and powering up? If so, this is not happening.

All eight solder joints on the top of the Chronodot look good. I have verified connectivity from the pins on the top of the Chronodot to the test points on the Blue board. I have verified that the battery has power. I have verified that the Chronodot and battery are installed in the orientation shown in the manual.

Any thoughts?





       
   
By: Windell (offline) on Thursday, December 31 2009 @ 12:57 AM PST  
Windell

Yes, definitely sounds as if it's not working correctly.

If you haven't yet tested either of these yet, verify that (1) with the Chronodot unplugged from the main board, BAT is 3 V above GND and (2) with the Chronodot plugged in, verify that you see 5 V between VCC and GND.

Next, verify that locations R12 and R13 on the circuit board are empty. A bad solder joint or accidental connection at pin 27 or 28 of the chip would definitely cause a problem like this. Visually inspect the solder joints, and verify that they aren't connected to power or ground or to each other.

You should probably inspect the pre-soldered pins of the RTC chip as well-- make sure that all of those connections look reasonable as well.

Now, in a case of simply *not finding the chronodot,* the clock should act like it isn't there-- that's case (1) that you listed. Cases 2 and 3 are much more worrisome-- this suggests that there's some kind of a short circuit or accidental connection being made, perhaps only when the Chronodot is plugged in.


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By: Anonymous: Steve () on Tuesday, January 05 2010 @ 08:13 PM PST  
Anonymous: Steve

I finally had some time to get back to this.

Prior to this above testing, I bent the Chronodot pins just a little to make sure that they were making good contact in their sockets. They had seemed a little loose even though all of the connections tested out good.

With the Chronodot unplugged, BATT is 3.1V above GND.
With the Chronodot plugged in, I see 5.3V between VCC and GND. I see 4.9V between SCL and SDA.

Positions R12 and R13 on the blue board are empty.

For the following tests I am using my multimeter's audible continuity setting to check connections.
There is no continuity between the two contacts of the R12 position.
There is no continuity between the two contacts of the R13 position.
There is no continuity between the left-side contacts of the R12 and R13 positions.
There is continuity between the two right-side contacts of the R12 and R13 positions and VCC on the Chronodot.

On the chip:
Pin 28 has continuity to the left contact of R12.
Pin 28 has continuity to SCL on the Chronodot.
Pin 28 has no continuity to any other pins on the chip.
Pin 28 has no continuity to Ground or VCC.

Pin 27 has continuity to the left contact of R13.
Pin 27 has continuity to SDA on the Chronodot.
Pin 27 has no continuity to any other pins on the chip.
Pin 27 has no continuity to Ground or VCC.

All solder joints on the chip look good. There are no visible bridges.

On the Chronodot:
BAT shows one-way continuity to RST, GND, VCC, SCL, and SDA.
All connections that I soldered have continuity to at least one pre-soldered pin on the Chronodot chip. GND connects to several. BAT has two-way continuity to one pin and one-way to most.
All connections (other than BAT) that I soldered have no continuity to any other connection that I soldered on the Chronodot.
All solder joints look good. All pre-soldered joints look good.
GND has continuity to GND on the main board.
VCC has continuity to VCC on the main board.


When the Chronodot is not present, the clock boots up as expected. (case 1 of my original message)
When the Chronodot is present, the clock does not boot up. No lights are present. There is no visible response to any momentary button push or to holding the buttons down. (case 2 of my original message)
When I am in Case 2, and I remove the chronodot while the clock is still powered up, then I go to case 3. The LEDs in the blue ring light up rapidly in sequence clockwise around the ring. They go partway around, turn off, then the clock boots up normally blinking 12:00.

In summary, the clock is still not working when the Chronodot is present.
Is there any testing that I can do to verify that my Chronodot is operating properly? Thanks.





       
   
By: Windell (offline) on Wednesday, January 06 2010 @ 04:11 AM PST  
Windell

Are you actually removing the Chronodot battery to do these tests? I ask because continuity testing is normally done with power off-- it can be unpredictable or even dangerous on a live circuit.

The only surprise that I notice in your measurements is the voltage at SCL and SDA. Both of those should be at 5 V with respect to ground, whether or not the Chronodot is connected. Please see if this is the case.

Is it possible that you-- perhaps in initial assembly -- momentarily set the battery on the Chronodot, but in the backwards position? It's easy to do, and the DS3231 chip is not tolerant of reverse voltage. (I'm not 100% certain that this would kill it, but it's a good guess. I would hate to sacrifice just one to be sure!)


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By: Anonymous: Steve () on Wednesday, January 06 2010 @ 11:16 AM PST  
Anonymous: Steve

While I don't remember temporarily setting the battery on the Chronodot the wrong way, it is at least theoretically possible that I did so.

I really do see a voltage difference between SCL and SDA when the clock is powered up.

With Chronodot installed and clock powered up:
Tested on the Chronodot Module:
SCL to SDA = 4.86V
SCL to GND = 0.46V
SDA to GND = 5.32V

Tested on the blue board:
The left contacts of R12 and R13 (which connect to SCL and SDA) are at 4.86V to each other.

When the Chronodot is removed and clock powered up:
Tested on the blue board:
The left contacts of R12 and R13 (which connect to SCL and SDA) are at 0.00V to each other.

Operating on the guess that my Chronodot might be bad, I have placed an order for a new one.





       
   
By: Windell (offline) on Wednesday, January 06 2010 @ 10:24 PM PST  
Windell

Hmm. Confused

Well, please let us know how it goes either way-- off forum might be best.


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By: Anonymous: Steve () on Sunday, January 10 2010 @ 04:49 PM PST  
Anonymous: Steve

My replacement Chronodot arrived yesterday, and I installed it today. It works correctly. Apparently my original was defective or I somehow managed to destroy it during the assembly process.





       
   



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