buyem said:
I haven't designed a circuit in more years then I care to mention so I
know I need help.
What I want to do is .. control a table saw and a shop vac.
When I turn the circuit ON...table saw and shop/vac on immediately
When I turn the circuit OFF... table saw off immediately and shop/vac to
run for approx. 5 seconds longer and then turn off.
If your able and/or willing to help I'll give you the specs for both
pieces of equipment.
A delay off relay has been suggested, and would be a
simple, but expensive, solution. Here's a "poor-man's"
solution that will cost < $20.00
TABLE SAW
---------------------------------------------
| Switch |
| / |
| AC Hot ---o o---+---------------------+ |
| | | |
| | ------- | |
| | | | | |
| +--| | | |---+ | |
| | o | | | |
| | | | | |
| ------- | [MOTOR]|
| | | | |
| AC Gnd ------------------+ | | |
| | | |
| AC Neutral ----------------------+------+ |
| |
---------------------------------------------
Wire up a junction box with a receptacle and
install on the table saw per the diagram above.
Plug a regulated 12V wall-wart supply into the
receptacle. Use the circuit below to operate a
relay which will control the vacuum.
a
+12 ---+----[D1]-----+----------+
| | |
[R1] [D3] |
| a| |
| a | |
+---[D2]------+ [Rly]
| | |
| + | |
[R2] [C1] |
| | |
| | |
Gnd ---+-------------+----------+
C1 = 1 Farad super cap CAT # CBC-17
Rly = Automotive 12V relay CAT # RLY-351
R1,R2 = 50 ohm, 25 W CAT # 50-25
Diodes = 1N4004 CAT # 1N4004
Wall Wart 12V regulated CAT # PS-1251
All parts from Allellectronics
http://www.allelectronics.com/
Some notes: R1,2 were picked based on availability
at Allelectronics. 5 watts would have been more than
adequate if they had that wattage.
The delay time is based on approximation. The exact
voltage that will allow the relay to drop out is
unknown, but should be about 2 volts. To shorten the
delay time, increase the value of R1 by adding power
resistors in series with R1. You might want to include
CAT # 16-5 in your order from Allelectronics.
That will give you three 16 ohm resistors for $1.00,
which you can add one at a time, as needed.
Your 12 volt supply *must* be regulated, and produce
no more than 12 volts. If it is not regulated, or
produces over 12 volts, add a second super cap in
series with C1. That will also shorten the delay
time.
Ed