Subject:
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Re: 5VDC Voltage Regulation
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Newsgroups:
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lugnet.robotics
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Date:
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Mon, 27 Sep 1999 18:26:14 GMT
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Viewed:
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599 times
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Ralph Hempel <rhempel@bmts.com> wrote in message
news:000001bf0901$f58c67a0$0500000a@pro150...
> > I'm in over my head with a project and need some help. I'm
> > trying to use an RCX
> > output port to control a 5VDC SPDT Relay from Radio Shack (part
> > #275-240A).
I would just put a 33Ohm 1/2W resistor in series with the relay coil.
According to the spec for the relay, the coil wants 5V at 90ma. The RCX
outputs about 8V with full power so that is 3V too much. The resistor must
eat up the 3V at 90ma. V/I=R so 3/.09=33 ohms. I^2 R=Power so (.09)^2
33=.27W so use a 1/2W. = RS#271-1104.
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Message has 2 Replies:
 | | RE: 5VDC Voltage Regulation
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| (...) Leave it to Michael to actually go through the math and put the right answer up for the group to see - nice work. Cheers, Ralph Hempel - P.Eng ---...--- Outside of a dog, a book is a man's best friend. Indside of a dog, it's too dark to (...) (25 years ago, 27-Sep-99, to lugnet.robotics)
| | | Re: 5VDC Voltage Regulation
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| (...) This doesn't seem to work. I am trying this first since it is the simplest solution so far and I have a 330hm resistor at hand. Without the resistor the voltage across the coil with he port set to level 7 is 7.17. When I add the resistor in (...) (25 years ago, 27-Sep-99, to lugnet.robotics)
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Message is in Reply To:
| | RE: 5VDC Voltage Regulation
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| (...) The RCX puts out a variety of waveforms depending on the power level. If you have acecss to an oscilloscope, you can see that the higher power levels give you more "on time" that lower levels. The DC level at full on is about a diode drop (...) (25 years ago, 27-Sep-99, to lugnet.robotics)
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