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Synchronar with SASM80

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Caruso

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Synchronar with SASM80

Post20 Mar 2012, 22:13

After many months of being outbid, I finally got hold of a stainless steel Sychronar with a SASM80 module. I'm really impressed with the design of the original watch from a technical point of view. The sealed module with magnetic switches, the solar power source and the functions of the watch show what a lot of thought has gone into it as a product designed for life rather than to appeal as the latest gadget. My colleagues at work are of the opinion it's the coolest watch in my collection now. Similarly, I'm impressed with the extra functions of the SASM80 module that allow you to format the display just how you want it - in my case Euro date format and 24hr time.

I do have a couple of questions not covered by the manual though.
The leap year number - is 4 the correct setting for 2012 as it's a leap year?
How long should the rechargeable batteries last between charges assuming normal usage?
How long should it take to recharge the battery in good sunlight?
Check out my vintage digital channel on YouTube:
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LED

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Re: Synchronar with SASM80

Post20 Mar 2012, 23:44

I have no informations about the SASM80 module, but I can give you some hints about the energy management:

First of all as with any other LED watch the display consumes a lot of power. With the the display continuously lit you may drain fully charged batteries within an hour or two. With display off the consumption can be called neglectable as it is lower than the self discharge rate of NiMh cells which will drain them within a few months anyway :!:

To fully recharge through the solar cells it may take 20 - 40 hours :!: :eek: in bright sunlight exposure, variations depending on the spezification of the solar cells and the rechargeables. And better take care that the watch won't get too hot under the sun.

Don't let the batteries sit fully discharged as this will ruin them fast. Best if you keep them always well charged, except once a year or so you may discharge them completely to prevent them from degrading through the so called memory effect.

When I restored my Synchronar I did not reglue the housing so I can open it anytime and I installed a batteryholder I made from a dead module holder so I can easily replace the cells or recharge them externally.
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Caruso

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Re: Synchronar with SASM80

Post21 Mar 2012, 00:19

Thanks, I guess the 2 hours it's had under a light won't have overcharged it then!
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abem

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Re: Synchronar with SASM80

Post21 Mar 2012, 01:43

Hi.

One obvious thought (which has probably already been proposed by every synchronar / SASM80 owner on the face of the planet). It would be nifty to have a micro USB port for quick charging from an outlet. It would probably make it impossible for the module to be sealed / waterproof, but it might be worth the trade off.

If only it were as quick and easy to implement ideas for projects as it is to come up with them.

-abe.
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LED

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Re: Synchronar with SASM80

Post21 Mar 2012, 01:53

I forgot to mention that there should practically be no risk of overcharging in the sense of damaging the batterys because the charge current / battery capacity ratio is too small for that.
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Re: Synchronar with SASM80

Post21 Mar 2012, 12:14

There´s a manual available on my website for the SASM80 module.

User LED wrote a nice summery. Dont´even try to charge the watch under a light. Riehl must have gotten a bunch of watches back and that´s why we now see all these inner parts from Barry popping up on ebay.

But let us take a look at the solar cell: The output of a modern silicium cell with the dimension of 100cm² (~40"x 40" inches) is round about 2 Ampere at 0,5 Volts in direct sunlight at 1000Watts/meter². But that would mean the solar cell is placed in a 90° angle to the sunbeams and there´s no red plastic cover above the cells and no sync-goo. Since P=VxA the output is 1Watt or 0,5W if the angle is not right with red top and so on. Now the solar cell has been produced in the 70s and has aged quite a bit, so I would say if you would use this 70s cell with a dimension of 100cm² (same as above), the output would be 0,25W at best. However the sync cell is just 20x25mm, so you have to multiply 0,25W with (20x25/100x100) which is 0,0125W. So the current flow in Ampere at 3Volts (a few cells are tied together in a row to archieve a 3V voltage) is... P/V=A..or 0,0125W/3V=0,0042A or 4,2mA. But we do not charge with 3V but just with 2,7V, because there´s a schottky diode between batteries and solar cell, so that the batteries cannot discharge through the solar cell. This diode takes 0,3V of the total voltage. The original module had a silicium diode in place (because these new schottkys weren´t available) so we would have a voltage drop of 0,7V.

Anyway let´s calculate the current flow with the schottky diode for the SASM80. We have 4,2mA x 2,7V/3V, thus 3,8mA.
Two V80 batteries (in case they are new) have an output of 80mAh at 2,8V which means you can power a circuit which takes 80mA at 2,8V for one hour. Let´s say the batteries are not completely drained an stll have an output of 30mAh at 2,8V , so that we would need to charge 50mAh.

We now search the time t until the batteries are full again. We can charge with 3,8mA at 2,7V. Now we look at the output P: P cell x h: 50mAh x 2,8V; P charge x h = 3,8mA x t [h] x 2,7V. Set P cell = P charge and calculate t.

t= 50mAh x 2,8V / (3,8mA x 2,7V) = 13,65h (in the sun!). Keep in mind that this a theoretical value with new batteries and no other losses. I recommend to charge the watch for at least 3 days in a row every month.

Hanno.
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Re: Synchronar with SASM80

Post21 Mar 2012, 20:48

SASM wrote:We now search the time t until the batteries are full again. We can charge with 3,8mA at 2,7V. Now we look at the output P: P cell x h: 50mAh x 2,8V; P charge x h = 3,8mA x t [h] x 2,7V. Set P cell = P charge and calculate t.
t= 50mAh x 2,8V / (3,8mA x 2,7V) = 13,65h (in the sun!)

IMO better calculate this based on charge (mAh), not energy (mWh) because there is no voltage converter, that is: solar cell current equals battery current, and solar cell minus Schottky diode voltage equals battery voltage.

So it boils down to:
Required charge of 50mAh and ~4mA solar cell (=charging) current take 50mAh/4mA = 12.5h charging time.
That was easy :-)


SASM wrote:Anyway let´s calculate the current flow with the schottky diode for the SASM80. We have 4,2mA x 2,7V/3V, thus 3,8mA.

That would be true with an ohmic load and a voltage-controlled source. But here we rather have a current-controlled source and a non-ohmic (constant voltage, similar to a z-diode) load, that is, the Shottky diode doesn't make much difference for the output curent (but only if the SC is actually run in the current-controlled region).
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Re: Synchronar with SASM80

Post21 Mar 2012, 21:04

Thanks Hanno for the reply, and for keeping these old watches going with production of new modules. :-D I specifically was looking for a watch with a SASM module as I always wear my vintage digitals, although they do sit in a case when not being worn.

I have downloaded the manual already from the website and found it very clear in helping me to set the date and time, to get the formatting to my liking and to set the trimming adjustment.

I was trying to make a video of my Synchronar last night, but it started acting strangely so I immediately suspected the batteries as I had been showing it off to a lot of people! I did manage to revive it by putting it under a light, but I would like to get it properly charged, and to maintain it in the long term. So thanks for that advice. Fortunately I have a window seat at work, so can leave my watch in the sun for charging a few days each month.
Check out my vintage digital channel on YouTube:
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Re: Synchronar with SASM80

Post21 Mar 2012, 21:50

Thanks rewolf for a correction. As said the main thing of this calculation is based on assumptions. In reality, things are even worse, because batteries aren´t fresh and have been stored for quite a while even if I got them new. I mean who needs V80 or V40 cells any more?

@ Caruso: I do not want to hide that I got some bad batteries with my last order. I know that because two costomers from Japan reported problems with their sunwatches about 4 days ago. It´s too bad that you cannot see that you have such a battery in your hands. If you are having problems with the synchronar or sunwatch, then just send it back. I just got a new battery lot and would replace and return it on my costs. It´s not that you definately got batteries from that lot, but just in case I want you to know that I will replace them since I give a warranty on all watch sales with SASM modules.

It´s a pity for me that the module is rarely the problem. To be honest I just had one broken micocontroller on a SASM80, the rest were empty batteries or a display which became defective or reed switches which reacted in a strange manner after some time. Moreover the return quote on sunwatches and synchronars is much higher than these of other modules (mostly broken original displays), so that I think to finish the SASM80/81/82 production. It just makes no sense if a customer cannot open the watch hisself to replace the batteries which is a construction fault of the case.

Hanno.
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Re: Synchronar with SASM80

Post21 Mar 2012, 22:09

........even with new batteries there are typically losses of between 10 and 50% in the battery as well. I took a look at your V80s and you need between 98mAh and 112mAh of charge current to actual pull them up to 80mAh capacity. So as long as you remain in the (almost) constant current region of the PV cells then Rewolfs 12.5 hours actually becomes 17.5 hours worst case.

[quote="SASM"]Keep in mind that this a theoretical value with new batteries and no other losses. I recommend to charge the watch for at least 3 days in a row every month.[/quote]

Regardless of how you get there this seems like a reasonable conclusion to me............

And seeing as I have my red pen out, 100cm2 does not equal 40" x 40" but 4" x 4". (Does anyone remember when that Mars(?) probe missed because NASA forgot how convert units M:)W:)M )

Nothing like some calculations to bring out the pedants eh?
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Re: Synchronar with SASM80

Post21 Mar 2012, 22:57

Hmm, well I am working with pedants all the day, so I am somewhat used to it. Most of them are also my friends :)
Regarding the unit conversion... I still have to put the unit conversion chart or calculator link back on this forum. Ed is already waiting... ~:( as just seen he has a reason.


By the way don´t analyse the calculations that much. It wanted to keep it simple. I also assumed that the cell output is at 3V which is not exactly right. Moreover it´s another problem to charge with a lower voltage than the output voltage of the battery. Just to mention these issues before I get further comments of further pedants :eek:
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Re: Synchronar with SASM80

Post22 Mar 2012, 00:18

Well I've got the video up on youtube now.

http://www.youtube.com/watch?v=3LyDWs4nYDI

Enjoy, and please feel free to correct any inaccuracies in the comments section.
Check out my vintage digital channel on YouTube:
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Re: Synchronar with SASM80

Post22 Mar 2012, 19:46

the math and tech formulas are awesome. for the non engineer mind [mine] i used v80 cells, synchronar sc, maybe some qc's, a little solder here and there, a burr to get the pcb to fit the red top and cells to fit the red bottom. for charging i put them under a lamp with a 100w bulb at about 1 foot [30cm? where is the converter when you need it?] for about 1 hr. from then on i either wear it or have them stored on a table top under a translucent skylight. i have rebuilt 14 of them. i still have some pcb's that probably will work, but no red tops, bottoms, or s/s case tops. i just glued another one together last night. i have taken to using a softer glue than epoxy which will make it more possible to reopen when necessary. i also have 1 mkII running on v40's for several years now with no ill effects. i did that and used a black bottom that i ground out to fit. all of mine are mkI/II's. i have never had to put any of them in the sun for hours at a time for charging. wearing should be sufficient. during times when they are not worn the are on the table under the skylight with no direct sunlight. 8-) :-D peter
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Re: Synchronar with SASM80

Post22 Mar 2012, 21:43

clockace wrote: i have never had to put any of them in the sun for hours at a time for charging. wearing should be sufficient. 8-) :-D peter


This obviously works nicely under the Arizona sun 8-) maybe not so well under the UK rain clouds. :lol:
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Re: Synchronar with SASM80

Post17 Nov 2013, 02:39

SASM wrote:There´s a manual available on my website for the SASM80 module.

User LED wrote a nice summery. Dont´even try to charge the watch under a light. Riehl must have gotten a bunch of watches back and that´s why we now see all these inner parts from Barry popping up on ebay.

But let us take a look at the solar cell: The output of a modern silicium cell with the dimension of 100cm² (~40"x 40" inches) is round about 2 Ampere at 0,5 Volts in direct sunlight at 1000Watts/meter². But that would mean the solar cell is placed in a 90° angle to the sunbeams and there´s no red plastic cover above the cells and no sync-goo. Since P=VxA the output is 1Watt or 0,5W if the angle is not right with red top and so on. Now the solar cell has been produced in the 70s and has aged quite a bit, so I would say if you would use this 70s cell with a dimension of 100cm² (same as above), the output would be 0,25W at best. However the sync cell is just 20x25mm, so you have to multiply 0,25W with (20x25/100x100) which is 0,0125W. So the current flow in Ampere at 3Volts (a few cells are tied together in a row to archieve a 3V voltage) is... P/V=A..or 0,0125W/3V=0,0042A or 4,2mA. But we do not charge with 3V but just with 2,7V, because there´s a schottky diode between batteries and solar cell, so that the batteries cannot discharge through the solar cell. This diode takes 0,3V of the total voltage. The original module had a silicium diode in place (because these new schottkys weren´t available) so we would have a voltage drop of 0,7V.

Anyway let´s calculate the current flow with the schottky diode for the SASM80. We have 4,2mA x 2,7V/3V, thus 3,8mA.
Two V80 batteries (in case they are new) have an output of 80mAh at 2,8V which means you can power a circuit which takes 80mA at 2,8V for one hour. Let´s say the batteries are not completely drained an stll have an output of 30mAh at 2,8V , so that we would need to charge 50mAh.

We now search the time t until the batteries are full again. We can charge with 3,8mA at 2,7V. Now we look at the output P: P cell x h: 50mAh x 2,8V; P charge x h = 3,8mA x t [h] x 2,7V. Set P cell = P charge and calculate t.

t= 50mAh x 2,8V / (3,8mA x 2,7V) = 13,65h (in the sun!). Keep in mind that this a theoretical value with new batteries and no other losses. I recommend to charge the watch for at least 3 days in a row every month.

Hanno.


I found this post as I wanted to compare the performance of my solar powered nixie watch with the Synchronar watch. I think the mentioned 3.8mA is still on the high side (I reckon it's only half of that). My panels are 31x11mm each and produce about 2mA @ 4.5V. I am charging 3.7V lipos. The required battery current to display the time in my watch is between 6mA (total darkness) and 200mA (any ambient light over 2,000 lux). Does anyone know how much current the Synchronar consumes in broad daylight? I estimated that with so many LED segments, it must be close to 80mA.

The mentioned series diode doesn't really matter, the open voltage of the solar panels is much higher than the rated 3V (probably close to 4.5V), so a 0.7V voltage drop over the series diode is neglectable. My panels are rated 4.5V but produce 7V in direct sunlight.

It's interesting that the Synchronar advertisements do not mention how much light is required to keep the battery charged. I am quite convinced that if you check the time about 30 times per day, you can't keep the battery charged. Does anyone have more information about that?

Best regards,
Michel

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