Search found 341 matches

by Ron H
Wed Oct 06, 2004 8:42 am
Forum: General Discussion
Topic: Current source
Replies: 64
Views: 16143

Re: Current source

<blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr>Originally posted by yigiter: i think i can not do this. because my grounded load is a "car battery" so i can't connect the positive side of my load to 0V.(12V->0V) and also i have not got a isolated power supply. i ha...
by Ron H
Wed Sep 29, 2004 12:12 pm
Forum: General Discussion
Topic: Large hysteresis circuit wanted.
Replies: 7
Views: 1488

Re: Large hysteresis circuit wanted.

You will find that pin 5 will only adjust the hysteresis over about a 0 to 100mv range. We need 4.5v of hysteresis, so I disabled the hysteresis control per the datasheet and used conventional positive feedback from the output to the noninverting input. BTW, I made the capacitor into the NPN base tw...
by Ron H
Tue Sep 28, 2004 12:44 pm
Forum: General Discussion
Topic: Large hysteresis circuit wanted.
Replies: 7
Views: 1488

Re: Large hysteresis circuit wanted.

This may be simpler, depending on your preferences.<p>Image
by Ron H
Tue Sep 28, 2004 9:07 am
Forum: General Discussion
Topic: Large hysteresis circuit wanted.
Replies: 7
Views: 1488

Re: Large hysteresis circuit wanted.

I think there may be an easier way than with the 556. What is the resistance of your relay coils - and inductance, if you know it.
by Ron H
Mon Sep 27, 2004 2:08 pm
Forum: General Discussion
Topic: Large hysteresis circuit wanted.
Replies: 7
Views: 1488

Re: Large hysteresis circuit wanted.

Hi Miguel, This may be too complex, but I think it will do what you want, based on simulation. The comparator (MAX921) resistor values are calculated, so you will have to pick the next closest value and/or trim them as required. I have never tried to post an image here before...<p> http://img6.exs.c...
by Ron H
Thu Aug 19, 2004 12:11 pm
Forum: General Discussion
Topic: Offset voltage on voltage follower
Replies: 19
Views: 5181

Re: Offset voltage on voltage follower

If you're using the CA3140's offset null to inject 0.5v offset, you're barking up the wrong tree. The offset null is meant to compensate for a few millivolts of offset error inside the op amp. The op amp may not even work correctly if you try to get 0.5v, and it certainly won't be temperature stable...
by Ron H
Wed Aug 04, 2004 11:13 am
Forum: General Discussion
Topic: Spice Question
Replies: 3
Views: 819

Re: Spice Question

What aspects of Nichrome do you want to model?
by Ron H
Wed Jul 28, 2004 10:28 am
Forum: General Discussion
Topic: sensing wall studs through tile over plaster and lath.
Replies: 14
Views: 2978

Re: sensing wall studs through tile over plaster and lath.

You may have already done a search. If so this is old news. The DIY sites on the Internet recommend using a studfinder with a metal mode. You look for a vertical row (OK, column) of nails. If you have metal lath, they recommend punching tiny holes near the baseboard (so repairs will be inconspicuous...
by Ron H
Sat Jul 10, 2004 8:16 pm
Forum: General Discussion
Topic: Capacitor to drop voltage...
Replies: 31
Views: 5914

Re: Capacitor to drop voltage...

Here's the schematic and the results of the simulation I mentioned: http://img40.exs.cx/img40/4631/LEDcurrentlimiter-NOT.gif http://img40.exs.cx/img40/5840/LEDcurrentlimiterwaves-NOT.gif <p>As you can see, the impulse currents are about 180ma. If you change the rise and fall times to 1us, the peak c...
by Ron H
Fri Jul 09, 2004 8:33 pm
Forum: General Discussion
Topic: Capacitor to drop voltage...
Replies: 31
Views: 5914

Re: Capacitor to drop voltage...

Even with parallel back-to-back diodes, you will get only high impulse currents at the pulse edges. Remember I=C*dv/dt. When dv/dt=0 (between transitions), no current will flow. Even with a 5v p-p sine wave, you get some strange-looking waveforms(I cheated - I ran a simulation). When the sine wave i...
by Ron H
Fri Jul 09, 2004 1:04 pm
Forum: General Discussion
Topic: linear output to logarithmic output?
Replies: 4
Views: 1216

Re: linear output to logarithmic output?

Actually, the voltage across the diode is proportional to the log of the current through the diode. The diode equation:<p>I=Is(e^(qV/kT)-1), where Is is the diode saturation (reverse leakage) current, q is the charge on an electron, k is Boltzmann's constant, and T is temperature in degrees Kelvin.<...
by Ron H
Fri Jul 09, 2004 11:15 am
Forum: General Discussion
Topic: linear output to logarithmic output?
Replies: 4
Views: 1216

Re: linear output to logarithmic output?

Do a Google search for "logarithmic amplifier". Also "log amp".<p>[ July 09, 2004: Message edited by: RonH ]</p>
by Ron H
Thu Jul 08, 2004 7:10 pm
Forum: General Discussion
Topic: frosted or diffused blue leds
Replies: 20
Views: 3941

Re: frosted or diffused blue leds

<blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr>Originally posted by cato: Tap, Tap, Tap....<p>Is this thing on?<hr></blockquote><p>LOL!<p> <blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr>DIGI-KEY SELLS BLUE LEDs IN T1 3/4 (5mm) BLU...
by Ron H
Tue Jul 06, 2004 10:04 am
Forum: General Discussion
Topic: dB and hfe
Replies: 13
Views: 2612

Re: dB and hfe

Dean, I think I got that right. I might take you up on that bluegrass offer though, even if you do send the dB cops after me. :) I do still have my CRC handbook - the copyright is 1959. I still use it occasionally, generally for trig identities, integrals, and differentials. The log and trig tables ...
by Ron H
Mon Jul 05, 2004 6:13 am
Forum: General Discussion
Topic: dB and hfe
Replies: 13
Views: 2612

Re: dB and hfe

<blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr>Originally posted by Dale Y: Yes, but not usually. hfe is current gain of just the transistor. Often dB is used to reference the gain of a circuit, the transistor, it's associated resistors capacitors inductors, and th...