DS12887 drop-in replacement

Discussion about old PC hardware.

Re: DS12887 drop-in replacement

Postby Maeslin » 2016-11-07 @ 01:23

gdjacobs wrote: (but fix that one blobby corner pin)!


That's the intent as soon as I get my tools back. :lol:
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Re: DS12887 drop-in replacement

Postby Half-Saint » 2016-11-08 @ 22:14

I managed to assemble one today but haven't got a CR1220 battery to test it.

As expected, I had trouble soldering the pins to the PCB. I wasn't using a socket but got these instead:
http://www.ebay.com/itm/172041044797?_t ... EBIDX%3AIT

Both of my problems might be due to a large soldering tip - sometimes I could smell the burnt plastic but mostly I could only get half of the hole to be filled with solder and I couldn't get the solder to spread evenly. The second problem is that some of the pins ended up lower than others probably due to heat.

One of the problems with castellation is that by cutting away the excess copper you risk damaging the pad. I actually managed to do exactly that on two pcbs. I used my fingers to wiggle the copper shavings...

The second problem for me is soldering "from the side" as you call it. What kind of soldering tip are you using and how exactly do you do this?

Again, I don't see how having a 2 mm wider PCB on the account of having proper holes would stop you from being able to insert the module? I have yet to see a motherboard that hasn't got 2 mm clearance on both sides of the RTC socket. Plus, it would be much easier to solder ;)

Thanks,
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Re: DS12887 drop-in replacement

Postby Maeslin » 2016-11-09 @ 00:24

Half-Saint wrote:The second problem for me is soldering "from the side" as you call it. What kind of soldering tip are you using and how exactly do you do this?

Again, I don't see how having a 2 mm wider PCB on the account of having proper holes would stop you from being able to insert the module? I have yet to see a motherboard that hasn't got 2 mm clearance on both sides of the RTC socket. Plus, it would be much easier to solder ;)

Thanks,
SainT


For the pictures posted at the end of the previous page I used a crappy no-name iron with no temperature control, with just a regular point tip. I just hold the iron tip in contact with the top of the stud for a few seconds and slowly feed solder. The castellated version of the board is really made for the specific socket mentioned in the parts list, since it depends on the diameter of the 'stub' being just right for the fit. Normal castellations have a much smaller hole size.

I've unfortunately worked on a board where the 'original' pcb (with through hole, not castellations) wouldn't fit due to width, so that's why I made the narrower castellated version.

A quick trick I found for assembly is to use loose perfboard as a support and guide to hold the socket (or strips of pins) upright and in the right position while soldering the pcb on top. It also helps prevent 'pin droop' when there's too much heat applied.
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Re: DS12887 drop-in replacement

Postby Maeslin » 2017-1-07 @ 20:37

For those interested, there's an updated version of the PCB that no longer relies on those castellated edges and is meant to work with regular 'square pin' 0.1" breakaway headers. Everything else is otherwise identical.

https://oshpark.com/shared_projects/qyNfzAMf
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Re: DS12887 drop-in replacement

Postby Shadow Lord » 2017-1-23 @ 10:39

Maeslin wrote:For those interested, there's an updated version of the PCB that no longer relies on those castellated edges and is meant to work with regular 'square pin' 0.1" breakaway headers. Everything else is otherwise identical.

https://oshpark.com/shared_projects/qyNfzAMf


Maeslin,

Whatever happened to the plans for a rechargeable version? Also are you planning on another run of fully assembled boards? Thanks!
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Re: DS12887 drop-in replacement

Postby Half-Saint » 2017-1-23 @ 21:35

I'm going to order 6-8 of the new PCBs for starters and see how those turn out. May have some assembled units ready next month.
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Re: DS12887 drop-in replacement

Postby Shadow Lord » 2017-1-25 @ 19:21

Half-Saint,

Are these going to have the rechargeable batteries? In either case I would be interested in a few maybe even five or six when you decide to order a production run. TIA!
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Re: DS12887 drop-in replacement

Postby Maeslin » 2017-1-25 @ 20:02

Shadow Lord wrote:Maeslin,

Whatever happened to the plans for a rechargeable version? Also are you planning on another run of fully assembled boards? Thanks!


I dropped the rechargeable option due to the difficulty in finding the rechargeable version of those coin cells and because putting a non-rechargeable cell in a rechargeable version could react badly. Besides, the rechargeable coin cells have much lower capacity than the non-rechargeable ones.

As for fully assembled boards, while I have a bunch here that are virtually ready to go I just haven't found a way to ship them for anything resembling reasonable rates. As it stands, shipping would be as expensive (or more expensive) as the unit itself and asking people to pay $15-$20 shipping for a $15 item is just ridiculous.


edit: Heh, looks like the module design has actually been making the rounds quite a bit in the Atari community, with people making their own and a guy in the Czech Republic blogging about it. Color me flattered. :D
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Re: DS12887 drop-in replacement

Postby NERocker » 2017-2-28 @ 09:41

I just had a 12887A chip go bad on me on a board inside a CNC controller in my shop - hadn't realized before this that there was such a thing as a chip embedded CMOS battery! If this were a socketed chip I would order your custom design even with $15 shipping in a heartbeat, unfortunately it is soldered to the board, so I am stuck with trying to mod it in place I guess - as I ponder this task, one thing keeps bothering me - how does the motherboard "know" that this battery is failing? on this chip the two pins (16&20) you have to hack to splice in a battery do not even exist, so it would seem the board has no way of measuring this voltage?
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Re: DS12887 drop-in replacement

Postby x689thanatos » 2017-3-07 @ 14:24

Very interresting.
At first i will solder a socket and hack the original chip but this custom board give a pretty neat résult.

NERocker wrote:I just had a 12887A chip go bad on me on a board inside a CNC controller in my shop - hadn't realized before this that there was such a thing as a chip embedded CMOS battery! If this were a socketed chip I would order your custom design even with $15 shipping in a heartbeat, unfortunately it is soldered to the board, so I am stuck with trying to mod it in place I guess - as I ponder this task, one thing keeps bothering me - how does the motherboard "know" that this battery is failing? on this chip the two pins (16&20) you have to hack to splice in a battery do not even exist, so it would seem the board has no way of measuring this voltage?


If you dont feel it, try on junk parts before or ask someone to help you. It's not that hard. Just dont do it first on something you care.
Because if you plan to hack the original chip directly on the board, you take the risk of damaging something else wich might be worse to répair because to acces pin 16 and 20 you have to grind spécific aera of the side of the chip.

the battery inside give power to a memory (also in the chip) to hold data your hardware need, even when there is no power from the network.
When the battery die, the memory inside of the chip cant hold anymore theses data. This is also why you cant read the voltage of the battery on the pins you can acces, because this battery is only for this memory, nothing else on your hardware.
The hack tell you where to grind the chip package to get acces to + and - to power the memory from an external cell, and the trace you have to cut on the side of the chip (after grinding) prévent the old dead battery to interact with the new. You still have to solder the pin of the battery holder where needed.

-On a computer this kind of chip keep bios settings, the bios can write them again, it's just without battery you might have every time "wrong date/time or bios settings" (just need to set bios settings again often).
-But there is also devices (like konami arcade board) where theses chip contains vital data that cant be restored when the battery died. the hardware wont work anymore, giving error or no boot at all.

in the first one you have to replace the battery in the way you want and it's OK
in the other... it's way more pain than just a new battery and some soldering.

Not sure in wish case the chip on your CNC machine is. But since theses machines cost à lot, you should consider asking someone who know exactly what to do.


PS : sorry for my bad english.
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Re: DS12887 drop-in replacement

Postby Half-Saint » 2017-5-12 @ 07:13

Well I finally received the PCBs and will start assembling the modules shortly. Anyone interested, let me know via PM.
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Re: DS12887 drop-in replacement

Postby deksar » 2017-5-23 @ 22:42

I am definitely interested in a few bunches of them, Half-Saint.
PM'd.
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Re: DS12887 drop-in replacement

Postby deksar » 2017-5-24 @ 11:34

Maeslin wrote:If someone wants the fully-finished version and doesn't mind shipping charges I can ship the ~20 I have assembled and tested as well.


Maeslin wrote:As for fully assembled boards, while I have a bunch here that are virtually ready to go I just haven't found a way to ship them for anything resembling reasonable rates. As it stands, shipping would be as expensive (or more expensive) as the unit itself and asking people to pay $15-$20 shipping for a $15 item is just ridiculous.

Maeslin, just like NERocker stated here, I'd definitely buy few too, no matter the costs.
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Re: DS12887 drop-in replacement

Postby matze79 » 2017-5-24 @ 18:08

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As you can see, it's already faulty here.
if you fixed it up, can you add it to dirtypcbs pcbshop ?
oshpark is far too expensive..
on dirtypcbs you get 10-12 for 12$.

i really would like to order a punch of this pcbs :) i also have a few machines wo need a proper Dallas Replacment.
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Re: DS12887 drop-in replacement

Postby BloodyCactus » 2017-5-24 @ 21:09

matze79 wrote:As you can see, it's already faulty here.


whats wrong with it that you think its faulty? the castellated edges are fine. some pins are n/c (hence no copper on a couple of through holes).
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Re: DS12887 drop-in replacement

Postby i486_inside » 2017-7-14 @ 15:12

I think I have an Idea for how you could put a higher capacity battery on it, instead of using a coin cell could it be possible to modify the design to hold a CR2 photo battery.
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Re: DS12887 drop-in replacement

Postby Maeslin » 2017-7-15 @ 11:35

matze79 wrote:As you can see, it's already faulty here.
if you fixed it up, can you add it to dirtypcbs pcbshop ?
oshpark is far too expensive..
on dirtypcbs you get 10-12 for 12$.

i really would like to order a punch of this pcbs :) i also have a few machines wo need a proper Dallas Replacment.


It's not actually faulty, the castellations are intentional to use with the socket mount that model of the PCB was intended for. There is another version available without the castellations. I can upload it to dirtypcbs.

i486_inside wrote:I think I have an Idea for how you could put a higher capacity battery on it, instead of using a coin cell could it be possible to modify the design to hold a CR2 photo battery.


That or a CR123A might be doable, but it would be a very tight fit and would make the adapter much higher. I'll check if it fits. Seems a bit overkill as even a 1220 should give ~5-10 years.
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Re: DS12887 drop-in replacement

Postby i486_inside » 2017-7-15 @ 17:40

I think I have thought of a cheaper way to do the whole thing, get a some DIP-24 DS12885 chips from allie express, get a really tiny SMT 6pf 32.768khz oscillator , then get some really sticky solder paste . then you could either try to place the oscillator between pins 2 and 3 from the side of the dip or maybe even on top of the pins, then you have to run wires to your battery holder then epoxy it into place then pot all the exposed wire in epoxy to protect it.
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Re: DS12887 drop-in replacement

Postby i486_inside » 2017-7-15 @ 17:52

I left out with solder paste my intention would be to reflow it in a reflow oven(or re purposed toaster oven.)
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Re: DS12887 drop-in replacement

Postby Maeslin » 2017-7-16 @ 20:27

i486_inside wrote:I think I have thought of a cheaper way to do the whole thing, get a some DIP-24 DS12885 chips from allie express, get a really tiny SMT 6pf 32.768khz oscillator , then get some really sticky solder paste . then you could either try to place the oscillator between pins 2 and 3 from the side of the dip or maybe even on top of the pins, then you have to run wires to your battery holder then epoxy it into place then pot all the exposed wire in epoxy to protect it.


To make things easier instead of working with solder paste and microscopic SMT oscillator, a simpler option might be to glue a surface-mount CR2/C123A battery holder on top of the DS12885 package (and run small wires to the correct pins), bend the clock pins 'up' instead of 'down', solder a 'can-size' crystal vertically to those pins and securing / hot-gluing the crystal to the side of the CR2/C123A battery holder.

something like this:
Code: Select all
      ___
     /   \   ┌─┐
   │( BAT )│▒│O│
   │ \___/ │▒│S│
   └───────┘▒│C│
  ╔═════════╗└╥┘
┌─╢ DS12885 ╟─╜
│ ╚═════════╝ │
│             │
with '▒' being adhesive. There would also be adhesive between the battery holder and the DS12885 but ASCII art has its limits.
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