Dave --
Conversely, if you just Google for AACircuit instead you'll get the same link to the homepage, but also the ability to translate it out of German if you're linguistically challenged like me.
Not wet, but that would be true only if you really need to keep full rated voltage across them for more than a few seconds. Once the solenoid armature has come into position, you may well be able to hold it there with far less than 12 V. The spec may tell you. It depends on whether what the solenoid moves applies a restoring force. If there isn't much of a 'push-back' force, you might need only 3 or 4 V to hold position. That would cut the power down a lot.
2 W and 12 V is 144/2 = 72 ohms. 3 V/72 ohms is 42 mA. 48 V times 42 mA is 2 W total for solenoid PLUS resistor.-- Regards, John Woodgate, OOO - Own Opinions Only. There are two sides to every question, except \'What is a Moebius strip?\' http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk
"Don A. Gilmore" schreef in bericht news:Czdee.37826$ snipped-for-privacy@tornado.rdc-kc.rr.com...
solenoids
then
must
Is is possible to connect it to 48V only, and switch from initial 100% duty cycle to something much lower duty cycle PWM, to drop to a current that is equal to 12V/Rsolenoid?
-- Thanks, Frank. (remove 'q' and 'invalid' when replying by email)
I had exactly that problem when automating a tape deck system (and it used exactly those same voltages).
Charge a large capacitor to 48 volts through a resistor selected to give sufficiently fast recharge but not so low as to dissipate large amounts of power when the solenoid is on.
Feed the top of the solenoid from the +ve of the capacitor and from the
+12v supply through a diode (anode to 12v, cathode to solenoid). Switch the bottom of the solenoid to ground by means of relay contacts (or a transistor able to cope with the maximum V and I)-- ~ Adrian Tuddenham ~ (Remove the ".invalid"s and add ".co.uk" to reply) www.poppyrecords.co.uk
Don't forget Mr. Diode:
D1 ------! ! !
D1 keeps the voltage from spiking up to a huge value when the switch turns off. Connecting it as shown causes the 36 or so volts on C1 to be the limit on the spike on the coil.
-- -- kensmith@rahul.net forging knowledge
Car fuel injectors are also pulsed to get them open quickly.
-- -- kensmith@rahul.net forging knowledge
I couldn't get the link to work, John. But you have piqued my curiosity.
Don Kansas City
The schematic has a gross error.
...Jim Thompson
-- | James E.Thompson, P.E. | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona Voice:(480)460-2350 | | | E-mail Address at Website Fax:(480)460-2142 | Brass Rat | |
-- If you don't, and you want to cut the wasted power to essentially zero, you might want to try something like this: news:ccvm71pbvs0hgn1155m6a1j36f308oi1pc@4ax.com
Can't you just add one more diode (D2 connected to +12V)? Then R can be made as large as possible, limited only by desired recovery time, and the resistor dissipation drops way down.....
D2 +----|
-- It's on alt.binaries.schematics.electronic under "Goosing a solenoid (from sed)".
Wouldn't that kind of depend on how good your +12 supply is at sinking reverse current?
Thanks, Rich
-- Then post what it is.
Aaaarghhh! Found it and fixed it. Thanks, Speff. :-)
-- John Fields Professional Circuit Designer
As it's shown it turns off faster, but the recycle time is slower... so pick your druthers ;-)
...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC\'s and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
Faithfully repeated in the next version.
Best regards, Spehro Pefhany
-- "it\'s the network..." "The Journey is the reward" speff@interlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com
can
time,
0Vsinking
Why? Provided C charges slowly, which it will, at release time the coil's supply node will be at 12v minus D2's drop. The flyback voltage seen by the driver then will be 12V-Vf(D2), plus D1's forward drop, or 12v.
Jim Thompson's arrangement turns the coil off faster. Recycle time isn't much different -- clamping by D2 prevents reverse-charging of C, so that node stays near 12v during flyback for both circuits.
Regards, James Arthur
Interesting pseudonym. The original "Dagmar" was a couple of years ahead of me in high school. The Egnor family barbershop... always good for an illegal poker game ;-)
...Jim Thompson
-- | James E.Thompson, P.E. | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona Voice:(480)460-2350 | | | E-mail Address at Website Fax:(480)460-2142 | Brass Rat | |
-- That will likely lead to the destruction of the switching device when the field around the coil collapses.
-- Oops... 'Cathode' doesn't mean 'Anode'...
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