Search found 71 matches
- Tue Sep 14, 2004 3:43 am
- Forum: General Discussion
- Topic: Transistor Relay Drivers
- Replies: 12
- Views: 5412
Re: Transistor Relay Drivers
Thanks Stephen, I'm still a little confused by the Vth, but I think I get the split resistor thing now. I think your saying that the low impedance the Capacitor would see makes for a very small time constant, so we need to use the split resistance to slow down the discharge of the cap. Right? Lookin...
- Mon Sep 13, 2004 12:55 pm
- Forum: General Discussion
- Topic: Transistor Relay Drivers
- Replies: 12
- Views: 5412
Re: Transistor Relay Drivers
jwax,
I see Vgs = 4 volts on figure 5 on this spec as 0 Amps regardless of Vds.MOSFETspec
I don't use MOSFET regularly so I could be wrong, but the threshold voltage doesn't look like full on to me. I guess I'm missing something.
-Rick
I see Vgs = 4 volts on figure 5 on this spec as 0 Amps regardless of Vds.MOSFETspec
I don't use MOSFET regularly so I could be wrong, but the threshold voltage doesn't look like full on to me. I guess I'm missing something.
-Rick
- Mon Sep 13, 2004 5:19 am
- Forum: General Discussion
- Topic: Transistor Relay Drivers
- Replies: 12
- Views: 5412
Re: Transistor Relay Drivers
In reverse order:<p>Hello, I don't think a Darlington is needed in this case I only need a ß of about 1.5.<p>JWAX, I don't think the Theshold Voltage turns a MOSFET on, it brings it to the threshold of on. In order to use an enhancement MOSFET and to open the channel Vs = 24, Vd = 0. I'm guessing I ...
- Fri Sep 10, 2004 12:33 pm
- Forum: General Discussion
- Topic: Transistor Relay Drivers
- Replies: 12
- Views: 5412
Transistor Relay Drivers
Are there any hazards associated with using a transistor to drive a 24VDC(coil) relay? Should I put a cap at the base to stop noise from activating my Relay? It seems like I should to me. Any thoughts?
-Rick
-Rick
- Thu Aug 26, 2004 2:28 pm
- Forum: General Discussion
- Topic: A watts question.
- Replies: 6
- Views: 3529
Re: A watts question.
Should be 'joules as energy' not 'joules and energy'.
- Thu Aug 26, 2004 2:20 pm
- Forum: General Discussion
- Topic: A watts question.
- Replies: 6
- Views: 3529
Re: A watts question.
I think of watts as Power and joules and energy. One interesting conversion is 1 horsepower = 746 Watts = 550 ft*lbs/sec. A watt can be thought of as energy spent over time which makes the watt-hour confusing, for me anyway. Serway says, "Power is defined as the time rate of energy transfer.&qu...
- Thu Aug 26, 2004 10:18 am
- Forum: General Discussion
- Topic: Current source
- Replies: 64
- Views: 29247
Re: Current source
Me, too.
-Rick
-Rick
- Tue Aug 24, 2004 3:36 am
- Forum: General Discussion
- Topic: Offset voltage on voltage follower
- Replies: 19
- Views: 9667
Re: Offset voltage on voltage follower
Stephen,<p>I like it. Much more elegant solution than my flailing produced. :) The buffered output circuit looks better to me though, in case the instrument turbo describes is an active load. He has the OPAMP, it would be a shame not to use it and the test circuit with the 1k load would work, too. -...
- Mon Aug 23, 2004 2:04 pm
- Forum: General Discussion
- Topic: Offset voltage on voltage follower
- Replies: 19
- Views: 9667
Re: Offset voltage on voltage follower
Ok, got it down to 6 resistors and one opamp if you have the plus and minus 5VDC sources. The general idea is the same as before. . . voltage divide the signal down to 3/5. Divide the -5VDC source to -0.5 and configure OPAMP as a difference amplifier with all of the resistors equal to 10k. I can sen...
- Mon Aug 23, 2004 1:39 pm
- Forum: General Discussion
- Topic: Offset voltage on voltage follower
- Replies: 19
- Views: 9667
Re: Offset voltage on voltage follower
I still think an adder will work. 1. voltage divide your dc source to 0.5 volts. If 5 VDC source 9k and 1k resistors. 2. voltage divide your 0-5 volts source down to 0-3 with a 2k and a 3k resistor. 3. add the two voltages for a 0.5 to 3.5 VDC output signal that track linearly with the 0-5 volt sour...
- Fri Aug 20, 2004 5:58 am
- Forum: General Discussion
- Topic: Offset voltage on voltage follower
- Replies: 19
- Views: 9667
Re: Offset voltage on voltage follower
Have you considered:
A 3/5 voltage divider for your 0-5 volt signal. Hoping for a 0-3 volt output.
Divide your DC voltage down to 0.5 VDC.
Then taking those two inputs into an OPAMP configured as an adder to get 0-3.5VDC out?
7 resistors and an OPAMP.
Would that work?
-Rick
A 3/5 voltage divider for your 0-5 volt signal. Hoping for a 0-3 volt output.
Divide your DC voltage down to 0.5 VDC.
Then taking those two inputs into an OPAMP configured as an adder to get 0-3.5VDC out?
7 resistors and an OPAMP.
Would that work?
-Rick
- Wed Aug 18, 2004 4:22 am
- Forum: General Discussion
- Topic: Current source
- Replies: 64
- Views: 29247
Re: Current source
Engineer, I think that might work, but I'd still like to avoid use of a pot.<p>Dale, Don't forget that alpha is beta dependent. α = ß/(ß+1) and the input of the current amplifier is the base the output of which is on the collector or emitter (Ic and Ie are nearly equal because as you pointed out α ~...
- Tue Aug 17, 2004 1:21 pm
- Forum: General Discussion
- Topic: Current source
- Replies: 64
- Views: 29247
Re: Current source
I figured it out a different way, but am still interested in other ideas.
-Rick
-Rick
- Tue Aug 17, 2004 12:48 pm
- Forum: General Discussion
- Topic: Engineering Mathematics
- Replies: 5
- Views: 2977
Re: Engineering Mathematics
My sympathies, the book I studied that stuff out of was called 'Complex Variables with Applications' by A. David Wunsch and it was the hardest class I ever took. The only advice I can offer is study hard, don't give up, work problems, work more problems and it will soon be over after you've worked e...
- Tue Aug 17, 2004 12:37 pm
- Forum: General Discussion
- Topic: Current source
- Replies: 64
- Views: 29247
Re: Current source
toejam, I don't think that will work. I need to smoothly change the output current from 0-250mA with a control input of 0-10 volts (the source of the 0-10 volts input can handle maybe 30mA max). I think the lm117 device would give me whatever current the load demands while maintaining a constant vol...