Vgs(max). Need to make sure sufficient Vgs to switch on Q1 at low
Vbat. Maybe two versions with different R1/R2?
+4/ Current Sensor resistor values. When building the first soldered
+prototype I found that residual flux messed up the 10M R11 feedback
+resistor. Scraping flux away and cleaning with solvent brought the
+resistance back up again. This could be a problem with home
+construction, and possibly humid environments. Perhaps we should
+scale resistors down to say 100k/10k voltage dividers, 1M R11?
+
+5/ When building the first soldered prototype I found that the
+position of the ground wires carrying high current caused the current
+sensor to stop working (stuck at 0V). U2 GND and the GND of R7, R9,
+R10 where at different places along the GND track carrying 0.5A. This
+caused a voltage drop of about 5mV between the two GNDs. I moved the
+ground connection (made the GND in GND out points close to each other
+so 0.5A was only flowing thru a short section of track) and the
+current sensor started working again. This suggests a carefully laid
+out PCB is a good idea.
+
+6/ The voltage on pins 2 & 3 of U2 (+/i op-amp input) should be within
+10 mV of each other with U2 unplugged. A greater difference indicates
+one of the resistor values is wrong.
+
TODO List
---------
+ with datasheet pdfs ?
[ ] wire correctly for power on reset
+ test with dodgy power on curve (slow power up)
+[ ] unused LM324 inputs
+ + check if its really OK to GND them
[X] blog post
[X] README in SVN
+ this file
[ ] check what happens in overvoltage on input, how can we protect?
[ ] document test plan
[ ] get PIC part name right in symbol file
+[ ] meausure the current consumption of the soldered prototype
+[ ] Indicate single point grounding on schematic
+[ ] Note 1% R's on schematic
[X] make sure we can't stall in RS232 input routine
+ need a way to get around this.....
+ malformed RS323 could cause a hang
+ or can it be spread over cycles?
[ ] enable PIC watchdog timer
+ how can we test?
+[ ] How repeatable is current sensor?
+ + y intercept (DC offset)
+ + slope
+ + maybe build a few a check
[ ] make sure all RS232 chars OK
+ how to prog with calibrated clock?
+ check baud rate
T 57500 35900 5 10 1 1 180 6 1
refdes=U2
T 58000 35600 5 10 0 0 180 6 1
-slot=2
+slot=1
}
C 56300 28300 1 0 0 lm324-1.sym
{
T 57000 29100 5 10 1 1 0 0 1
refdes=U2
T 56300 28300 5 10 0 0 0 0 1
-slot=1
+slot=2
}
C 56300 29300 1 0 0 lm324-1.sym
{
}
C 54400 36300 1 270 0 bf-resistor-1.sym
{
-T 53900 36000 5 10 1 1 0 0 1
+T 54700 36000 5 10 1 1 0 0 1
refdes=R6
-T 53900 35800 5 10 1 1 0 0 1
-value=1M
+T 54700 35800 5 10 1 1 0 0 1
+value=100k 1%
}
C 54400 34900 1 270 0 bf-resistor-1.sym
{
-T 53900 34700 5 10 1 1 0 0 1
+T 54700 34600 5 10 1 1 0 0 1
refdes=R7
-T 53900 34500 5 10 1 1 0 0 1
-value=100k
+T 54700 34400 5 10 1 1 0 0 1
+value=10k 1%
}
C 56400 36300 1 270 0 bf-resistor-1.sym
{
-T 55900 36000 5 10 1 1 0 0 1
+T 56700 36400 5 10 1 1 0 0 1
refdes=R8
-T 55900 35800 5 10 1 1 0 0 1
-value=1M
+T 56700 36200 5 10 1 1 0 0 1
+value=100k 1%
}
C 56400 34900 1 270 0 bf-resistor-1.sym
{
-T 55900 34600 5 10 1 1 0 0 1
+T 56700 34600 5 10 1 1 0 0 1
refdes=R9
-T 55900 34400 5 10 1 1 0 0 1
-value=100k
+T 56700 34400 5 10 1 1 0 0 1
+value=10k 1%
}
C 57500 34900 1 270 0 bf-resistor-1.sym
{
-T 57000 34600 5 10 1 1 0 0 1
+T 57800 34100 5 10 1 1 0 0 1
refdes=R10
-T 57000 34400 5 10 1 1 0 0 1
-value=10M
+T 57800 33900 5 10 1 1 0 0 1
+value=1M 1%
}
C 58000 36000 1 0 0 bf-resistor-1.sym
{
T 58300 36500 5 10 1 1 0 0 1
refdes=R11
T 58300 36300 5 10 1 1 0 0 1
-value=10M
+value=1M 1%
}
N 54500 36700 54500 36300 4
N 54500 35400 54500 34900 4