Search found 1549 matches

by dyarker
Sat Oct 25, 2003 6:42 am
Forum: General Discussion
Topic: Is it possible to parallel transformers
Replies: 17
Views: 2712

Re: Is it possible to parallel transformers

The thing to watch when paralleling transformers is getting the phase right. Two identicle transformers probably have the same relative phases on the leads.<p>To check, connect the primaries in parallel, then one lead of the secondaries. Apply signal to the primary. The two open secondary leads shou...
by dyarker
Thu Oct 23, 2003 10:58 pm
Forum: General Discussion
Topic: stable clock timer..for a different LED clock
Replies: 18
Views: 3521

Re: stable clock timer..for a different LED clock

Instead of resistor divider, use resistor to a 5.1V or 4.7V zener to ground after the diode connected to a transformer lead (low voltage side of course). That gives squarer pulses. A low value capacitor in parallel with the zener filters power line noise and thermal noise generated by the zener.<p>I...
by dyarker
Tue Oct 21, 2003 8:24 pm
Forum: General Discussion
Topic: stable clock timer..for a different LED clock
Replies: 18
Views: 3521

Re: stable clock timer..for a different LED clock

For real reliability use the 60Hz power line for the frequency source, and divide a crystal oscillator to 60Hz. Then when the power goes off, batteries provide backup power, and a missing pulse detector switches in the crystal pulses until 60Hz power returns. Putting battery power to the LEDs throug...
by dyarker
Sat Oct 18, 2003 7:51 pm
Forum: General Discussion
Topic: Problem with motorhome lighting
Replies: 7
Views: 1187

Re: Problem with motorhome lighting

I agree with sundancer87, there is a problem. Those transistors are large enough to drive head lights.
by dyarker
Fri Oct 17, 2003 9:14 pm
Forum: General Discussion
Topic: Problem with motorhome lighting
Replies: 7
Views: 1187

Re: Problem with motorhome lighting

Even big transistors need resistors in series with the base.<p>Or, If the wires from the transistors to the lamps have worn insulation, going over bumps could have caused a short. That could have caused an emitter/collector short. The lamps stay on when the vehicle is still or on smooth road.<p>Or, ...
by dyarker
Sat Oct 11, 2003 10:55 pm
Forum: Robotics
Topic: Stamp reading RC Receiver signal to servo
Replies: 2
Views: 1931

Re: Stamp reading RC Receiver signal to servo

I've never worked with servos (yet), but I recognize the symptoms.<p>A micro-controller input has a very high impedance (probably CMOS). Add a resistor from signal line to ground, to increase the load on the RC receiver to something closer to what it expects to drive. I'd start at 10K Ohms.<p>It may...
by dyarker
Sat Oct 11, 2003 10:16 pm
Forum: General Discussion
Topic: Help Micro Circuit - 1 button switch to 3 led cycle cant
Replies: 6
Views: 1611

Re: Help Micro Circuit - 1 button switch to 3 led cycle cant

**Moved from Robotics Forum** I think it nearly impossible within 10mm x 50mm because blue LEDs need 3.9V to 4.5V. Including the current limiting resistor you'll need 5.5 to 6 volts. ______________________________ Proposed - Two AA cells in series. A circuit board the same width as AA diameter. On o...
by dyarker
Sat Oct 11, 2003 10:11 pm
Forum: General Discussion
Topic: Signal sensing circuit
Replies: 5
Views: 1413

Re: Signal sensing circuit

250 ft. is a L O N G way to go for a microphone. Does the mic work, without hum, when connected close to paging amp? Is the PA input labeled "MIC"? You can't just parrallel the mic with the phone system line either.<p>What kind of plug on the mic? Three conductor with push-to-talk switch sharing one...
by dyarker
Fri Oct 10, 2003 1:11 am
Forum: Robotics
Topic: Help Micro Circuit - 1 button switch to 3 led cycle cant
Replies: 2
Views: 2112

Re: Help Micro Circuit - 1 button switch to 3 led cycle cant

**Moved to same topic in General Forum**<p>[ October 11, 2003: Message edited by: Dale Y ]</p>
by dyarker
Thu Oct 09, 2003 11:35 pm
Forum: General Discussion
Topic: Signal sensing circuit
Replies: 5
Views: 1413

Re: Signal sensing circuit

Did you spell "Convayent" correctly? A search on Google resulted in ZERO hits. It's possible the company doesn't have a web site, but very unlikely that NOBODY is talking ABOUT them. So much for just looking it up and giving you an exact answer.<p>And, since you're asking here, I assume the manual i...
by dyarker
Thu Oct 09, 2003 9:16 pm
Forum: General Discussion
Topic: Reverse Polarity Catch 22
Replies: 3
Views: 996

Re: Reverse Polarity Catch 22

If Unit A's power supply is floating (circuit ground not connected to earth), then a single diode in SERIES in A's power in is enough. Almost no current flows, so everything is protected. (Think bird sitting on power line. His feet might be at 10000 Volts; but so is his head as long as he doesn't to...
by dyarker
Thu Oct 09, 2003 6:03 am
Forum: General Discussion
Topic: Signal sensing circuit
Replies: 5
Views: 1413

Re: Signal sensing circuit

Use a loop-start trunk card instead of a line card on the PBX for the paging system. A CO trunk will also work. Lines or trunks from PBXs are 600 Ohm balanced, not 1 Volt line. (A 600 Ohm to 10KOhm transformer can fix that.) Current through an opto-coupler LED to sense selected.<p>If, on the other h...
by dyarker
Tue Sep 30, 2003 9:26 pm
Forum: General Discussion
Topic: RPM regulation
Replies: 55
Views: 10126

Re: RPM regulation

The generator controller will control the output voltage via the current it feeds the field winding. You need to maintain constant engine RPM for about 60Hz out.<p>A cruise control isn't exactly right because they measure RPM after the tranmission, and try to keep the wheel RPM the same as when the ...
by dyarker
Thu Sep 25, 2003 12:50 am
Forum: General Discussion
Topic: Resistor Nomenclature
Replies: 4
Views: 1165

Re: Resistor Nomenclature

Dean,<p>That's interesting. All this time I thought the printing company didn't have the omega character in their machine.
by dyarker
Wed Sep 24, 2003 5:10 am
Forum: General Discussion
Topic: Need to reduce 4 volts to 3 volts
Replies: 9
Views: 2007

Re: Need to reduce 4 volts to 3 volts

Sounds like the 1 Ohm resistor is parallel with the load, instead of in series. THAT will eat batteries!<p>Did you measure the current yet? And, what KIND of load?