Battery charger system using a SX using the "ANALOGIN" command
OzStamp
Posts: 377
Hi All.
Will be·doing a little project that·requires monitoring a battery.
Reading thru the SXB online doc that we just printed out ..
It occurs to me that it would be easy to accomplish that using the
schematic on page 37..
With monitoring a battery we mean charge it when needed..
So if the voltage across the battery terminals falls below a certain value
start charging and when the voltage reaches the max voltage allowed
across the battery .. stop charging..or maybe even trickle charge...
Some of the commercially available chips from MAXIM ( 712/713) and many other
from vendors like LTC··· SGS etc· are not readily available and now with the
low cost of the SX chips .. that sounds like a good application for them.
Has anybody already been down this path and willing to share their findings.
I will be exploring this issue in depth so will share what we find as time goes on.
Cheers
Ronald Nollet·· Australia
Will be·doing a little project that·requires monitoring a battery.
Reading thru the SXB online doc that we just printed out ..
It occurs to me that it would be easy to accomplish that using the
schematic on page 37..
With monitoring a battery we mean charge it when needed..
So if the voltage across the battery terminals falls below a certain value
start charging and when the voltage reaches the max voltage allowed
across the battery .. stop charging..or maybe even trickle charge...
Some of the commercially available chips from MAXIM ( 712/713) and many other
from vendors like LTC··· SGS etc· are not readily available and now with the
low cost of the SX chips .. that sounds like a good application for them.
Has anybody already been down this path and willing to share their findings.
I will be exploring this issue in depth so will share what we find as time goes on.
Cheers
Ronald Nollet·· Australia
Comments
Other than that, it should work. You might want to also monitor the battery temperature so you can stop charging if the battery gets too hot.
Bean.
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·
Prototyped the circuit and used various methods monotoring the voltage.
Using the analogin method we get very noisy readings..
Stuffed around with lots of dif caps and settings.. aborted that...
Tried the PWM ADC principle .. works good .. well enough for the application.
Stumbled across another method .. really very simple.
As we have done this many years ago but we did not use a micro just some
voltage comparators to sense various levels and windows to trigger the charging ..
etc etc ... all simple stuff..
The micro will do other stuff as well.. not just monitor the battery...
Now here is a trick
Using the compare command.
Setup the circuit as per page 47 in the onLine help manual.
Use 3 line program..and also add 1 additianal resistor from RB.O·to the centre
point (V Threshold on RB.2) of the 2 resistors.
Effectively creating some hysteresis..also use RB.0 to signal the circuit for charging..
Some more components needed.. but for simplicity did not add all that stuff..
Thinking about adding the temp monitoring as well... thanks Terry.
So now the RB.O comes on at 1.9 V and goes off at 3.0V.
Awesome exactly what we need... no caps no tuning .. fricking simple..
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<<· Measure volts here
Cheers·· Ronald Nollet·· Australia