Search found 14 matches

by doctorb5
Wed Jun 04, 2003 12:46 pm
Forum: General Discussion
Topic: DC amps versus AC amps
Replies: 6
Views: 1353

Re: DC amps versus AC amps

Yes, that's what I ended up doing. I paid about $4 for a 20 Amp DPDT switch at Radioshack. But I enjoyed learning about the reasons why I shouldn't use a strictly AC switch. :)
by doctorb5
Mon Jun 02, 2003 2:42 pm
Forum: General Discussion
Topic: DC amps versus AC amps
Replies: 6
Views: 1353

Re: DC amps versus AC amps

Thanks for the "short" answer... ;) <p>I'll give you more details if you want: The switch is going to be used as a cutoff switch for a 24 Volt system. The system starts with two 12 Volt, sealed lead-acid batteries in series. They feed an electronic (PWM) speed controller that powers two 12 Volts DC ...
by doctorb5
Mon Jun 02, 2003 11:56 am
Forum: General Discussion
Topic: DC amps versus AC amps
Replies: 6
Views: 1353

DC amps versus AC amps

Hi all,<p>This has probably been answered before, but I thought I'd try to get a fresh perspective. I need to switch a 24volt, 10A current. I went to my local hardware store and found lots of switches that can carry a 10 or 20A load. But they are all rated for an AC current. Actually, the ones that ...
by doctorb5
Tue May 06, 2003 10:49 am
Forum: General Discussion
Topic: Diode or no diode?
Replies: 9
Views: 1902

Re: Diode or no diode?

Whoa! Have you ever had a day when you wanted to ask what you though was a simple question and ended up discovering a whole new world? Well, after reading all this very instructive stuff, I feel just like that... :) <p>I think I understand most of what was said, and I will definitely use the diodes....
by doctorb5
Mon May 05, 2003 11:43 am
Forum: General Discussion
Topic: Diode or no diode?
Replies: 9
Views: 1902

Re: Diode or no diode?

Thanks Lien.<p>You are correct, the diode is in parallel with the motor and prevents current from reversing during the "cut-off" period of the PWM. But, correct me if I'm wrong, a MOSFET has a diode between Source and Drain that would prevent any of those transient currents from coming back. (I'm no...
by doctorb5
Mon May 05, 2003 11:03 am
Forum: General Discussion
Topic: Diode or no diode?
Replies: 9
Views: 1902

Diode or no diode?

Hello,<p>I am building a DC speed controller for a 24 volt motor. The controller is based on a PIC 16F84 that drives a couple of IRLZ44N FET's. The speed variation is achieved with the PWM method. The frequency of the PWM is about 2000 Hz, and the motor draws about 5 to 10 amps.<p>My question has to...
by doctorb5
Fri Jun 14, 2002 7:59 am
Forum: General Discussion
Topic: Electronic locomotive whistle
Replies: 14
Views: 5828

Re: Electronic locomotive whistle

I can't thank you enough Tim!!! This is exactly what I've been looking for. Thanks also for your help via email. :)
by doctorb5
Fri Jun 14, 2002 7:57 am
Forum: Robotics
Topic: A little help with MOSFETs and PIC
Replies: 5
Views: 2501

Re: A little help with MOSFETs and PIC

Thank you Ron! :)
by doctorb5
Wed Jun 12, 2002 2:46 pm
Forum: Robotics
Topic: A little help with MOSFETs and PIC
Replies: 5
Views: 2501

A little help with MOSFETs and PIC

Hello everyone!<p>In the January 2001 issue of Nuts & Volts there was a DC motor speed controller based on a PIC12C671 driving a single MOSFET (ref IRL540). The text says that the controller can handle up to 28 Amps and 18 Volts.<p>I am working on a similar project, but the main voltage will be 24 V...
by doctorb5
Mon May 20, 2002 5:46 am
Forum: General Discussion
Topic: Electronic locomotive whistle
Replies: 14
Views: 5828

Re: Electronic locomotive whistle

Well, it's been 2 weeks and I haven't heard anything from that Australian company about their whistle. I guess it wasn't what I needed... :( <p>On the other hand, I have found a site that describes an algorithm to get sound from a PIC using a 1-bit technique. You can even download a DOS program that...
by doctorb5
Mon May 06, 2002 7:55 am
Forum: General Discussion
Topic: Electronic locomotive whistle
Replies: 14
Views: 5828

Re: Electronic locomotive whistle

Those are great suggestions! Thanks.<p>- James: I thought of that too, but I am not very good at audio theory. You see, I can easily make a "European" steam whistle. Those are high-pitch, single-tone whistles. You can even make a simple one with an NE555. On the other hand, American steam whistles a...
by doctorb5
Fri May 03, 2002 1:22 pm
Forum: General Discussion
Topic: Electronic locomotive whistle
Replies: 14
Views: 5828

Re: Electronic locomotive whistle

Thanks Chris. The Yamaha chips look very nice, but out of my budget. On the other hand, I've found the SN9428 on the RadioShack site. Maybe I can still find it on the Net. :)
by doctorb5
Thu May 02, 2002 8:40 am
Forum: General Discussion
Topic: Electronic locomotive whistle
Replies: 14
Views: 5828

Re: Electronic locomotive whistle

Thanks for the info. I did a quick search on Digikey's site and was not successful. Any other sources? Also, I've never played with those chips. Do they come with some kind of docs? or would you have a sample application or a link to a project utilizing the chips?<p>Thanks. :)
by doctorb5
Wed May 01, 2002 1:33 pm
Forum: General Discussion
Topic: Electronic locomotive whistle
Replies: 14
Views: 5828

Electronic locomotive whistle

I'd like to make an electronic steam train whistle for a project that I have. I have looked around and found "sound on chip" solutions that do not work exactly as I'd like. Specifically, I'd like to have more control over the duration of the sound than those chips provide. What I envision is a whist...