DS1302 Back-up Battery Charger

Nick Waldvogel · 2010-03-03 21:16

I have been working with a DS1302 and I can't seen to get the coding right to turn off the charging output. I read the data sheet and it states that the output is off by default. However, I somehow got it turned on because I have a output voltage of 1.20v on the back-up pin. I want to be able to turn it off so that I don't have trouble with non-rechargeable batteries. I just need a shove in the right direction. Thanks for any input.

Nick

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sam_sam_sam · 2010-03-04 00:26

Here is the table that you need

'

Trickle Charge values

Tric····· CON %10010000
OFF······ CON %11110000 'turns off trickle charge
D1R1····· CON %10100101 '1 diode 1 resistor 0.7v 2k ohms
D1R2····· CON %10100110 '1 diode 2 resistor 0.7v 4k ohms
D1R3····· CON %10100111 '1 diode 3 resistor 0.7v 8k ohms
D2R1····· CON %10101001 '2 diode 1 resistor 1.4v 2k ohms
D2R2····· CON %10101010 '2 diode 2 resistor 1.4v 4k ohms
D2R3····· CON %10101011 '2 diode 3 resistor 1.4v 8k ohms
Temp = D2R3············ ' *** Edit this variable ***
RTCCmd = TRIC

How ever you would be better off to us a ONE FARD Supper Cap work much better I have used both

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··Thanks for any·

·that you may have and all of your time finding them

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Sam

Nick Waldvogel · 2010-03-04 03:08

Thanks for the reply Sam

I have tried to use te values you provided. I still can't get it to work. Maybe I'm testing it wrong? I'm testing with a DVM from Vss to pin #8 of the DS1302 with the battery not installed. I thought I was getting 1.20v but as I test more and more I find that the voltage is moving around..... I have seen voltage as high as 4.20v and the lowest I can get now is 1.7 volts. I have stripped the code down to what I believe is the bare minimum to get it to change the charger settings.

' {$STAMP BS2}
' {$PBASIC 2.5}

'------- Trickle Charge values ---------------------------------------------
Tric      CON %10010000
OFF       CON %00001111 'turns off trickle charge
D1R1      CON %10100101 '1 diode 1 resistor 0.7v 2k ohms
D1R2      CON %10100110 '1 diode 2 resistor 0.7v 4k ohms
D1R3      CON %10100111 '1 diode 3 resistor 0.7v 8k ohms
D2R1      CON %10101001 '2 diode 1 resistor 1.4v 2k ohms
D2R2      CON %10101010 '2 diode 2 resistor 1.4v 4k ohms
D2R3      CON %10101011 '2 diode 3 resistor 1.4v 8k ohms
Temp = D2R2            ' *** Edit this variable ***
RTCCmd = TRIC



' -----[noparse][[/noparse] I/O Definitions ]-------------------------------------------------

DataIO          PIN     0               ' DS1302.6
Clock           PIN     1               ' DS1302.7
CS1302          PIN     2               ' DS1302.5


' -----[noparse][[/noparse] Constants ]-------------------------------------------------------

CWPr            CON     $8E             ' Write Protect Register
WPr1            CON     $80             ' Set Write Protect
WPr0            CON     $00             ' Clear Write Protect


' -----[noparse][[/noparse] Variables ]-------------------------------------------------------

reg             VAR     Byte            ' Read/Write Address
ioByte          VAR     Byte            ' Data To/From DS1302


Temp      VAR Byte
RTCCmd    VAR Byte


  reg = CWPr                            ' Initialize DS1302
  ioByte = WPr0                         ' Clear Write Protect
  HIGH CS1302                           ' Select DS1302
  SHIFTOUT DataIO, Clock, LSBFIRST, [noparse][[/noparse]reg, ioByte]
  LOW CS1302                            ' Deselect DS1302
  HIGH CS1302                           ' Select DS1302
  SHIFTOUT DataIO, Clock, LSBFIRST, [noparse][[/noparse]%10010000, %00001111]
  LOW CS1302                            ' Deselect DS1302


 STOP

Nick

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Nick Waldvogel · 2010-03-04 03:25

I now relize that when I change the value highlighted I get a voltage change on pin #8. I get 4.10v with a value of %10101011 and 1.60v with %10101011.

I'm concerned that even with a value of %00001111 it should turn off the charging output but I still get a voltage above 1 volt. Maybe it's nothing to be worried about?

HIGH CS1302                                                                      ' Select DS1302
  SHIFTOUT DataIO, Clock, LSBFIRST, [noparse][[/noparse]reg, ioByte]
  LOW CS1302                                                                              ' Deselect DS1302
  HIGH CS1302                                                                             ' Select DS1302
  SHIFTOUT DataIO, Clock, LSBFIRST, [noparse][[/noparse]$90, [b]%10101011[/b]]
  LOW CS1302                                                                              ' Deselect DS1302

Nick

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Nick Waldvogel · 2010-03-04 03:56

With even more testing I found that the mA are changing as they should, based on the formula provided on the data sheet, with a battery installed. I believe that the battery needs to be low on voltage to see the voltage change. Everything seems to be falling into place.

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sam_sam_sam · 2010-03-04 22:26

Make sure that you only use about 100 millamp hour batterys if the millamps are more than that··they may not charge all the way up

The ones that a cordless phone battery pack this is what I would

That why I was saying that I use supper caps

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··Thanks for any·

·that you may have and all of your time finding them

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Sam

Post Edited (sam_sam_sam) : 3/4/2010 10:33:20 PM GMT

DS1302 Back-up Battery Charger

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