Sorta OT: Safety Issues (UPS idea)
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Ugh! Microsoft Outlook completely scrambled the simple schematic I'd just
sent. Here's attempt #2...
Idea for a simple UPS (uninterruptible power supply) for a Stamp: (use
Courier New font to display properly)
. R3
.To Stamp logic input A o
WWW
+
. |
. CR1 |
. To Stamp Vcc o
+----|<
+
o To power supply +5v
. | |
. | |
. - |
. CR2 A |
. | |
. R2 | R1 |
.To Stamp logic input B o-WWW-+----WWW----+
. |
. |
. C1 ===
. |
. |
. -
. V (ground)
CR1 & CR2; general-purpose rectifier diodes, 10+PIV, >500mA
R1: 470 ohm, 1/4 watt, allows charging C1 at a 10mA rate. Don't charge the
cap too quickly!
R2 & R3: 2k ohm, 1/8 watt, prevents inadvertent burn-out of Stamp circuits
should the ports be selected for output and driven low.
C1: a big electrolytic capacitor. 10,000 uF @ 6.3 volts should be
sufficient, but it won't hurt to use a larger one.
Theory of Operation:
Power is turned on, Stamp receives Vcc and 5v on logic input "A" (choose
which data input you'd like to monitor). Stamp begins monitoring logic
input "B" for voltage level; continues to test voltage level and sleep in a
loop until sufficient voltage is available for emergency backup operation.
If during this loop logic input "A" drops to zero, Stamp enters "sleep"
mode.
Once acceptable voltage level exists on input "B", the Stamp program should
go about housekeeping chores and monitoring your controlled device(s). The
program should periodically check the logic level on input "A"; if it's
dropped to zero, save all program variables in external static RAM
(preferred) or to the internal Eeprom (limited life cycle), then enter
"sleep" mode.
sent. Here's attempt #2...
Idea for a simple UPS (uninterruptible power supply) for a Stamp: (use
Courier New font to display properly)
. R3
.To Stamp logic input A o
WWW
+
. |
. CR1 |
. To Stamp Vcc o
+----|<
+
o To power supply +5v
. | |
. | |
. - |
. CR2 A |
. | |
. R2 | R1 |
.To Stamp logic input B o-WWW-+----WWW----+
. |
. |
. C1 ===
. |
. |
. -
. V (ground)
CR1 & CR2; general-purpose rectifier diodes, 10+PIV, >500mA
R1: 470 ohm, 1/4 watt, allows charging C1 at a 10mA rate. Don't charge the
cap too quickly!
R2 & R3: 2k ohm, 1/8 watt, prevents inadvertent burn-out of Stamp circuits
should the ports be selected for output and driven low.
C1: a big electrolytic capacitor. 10,000 uF @ 6.3 volts should be
sufficient, but it won't hurt to use a larger one.
Theory of Operation:
Power is turned on, Stamp receives Vcc and 5v on logic input "A" (choose
which data input you'd like to monitor). Stamp begins monitoring logic
input "B" for voltage level; continues to test voltage level and sleep in a
loop until sufficient voltage is available for emergency backup operation.
If during this loop logic input "A" drops to zero, Stamp enters "sleep"
mode.
Once acceptable voltage level exists on input "B", the Stamp program should
go about housekeeping chores and monitoring your controlled device(s). The
program should periodically check the logic level on input "A"; if it's
dropped to zero, save all program variables in external static RAM
(preferred) or to the internal Eeprom (limited life cycle), then enter
"sleep" mode.