ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals
ECN Shout Chat
ShoutChat
Recent Posts
Increasing demand factors in residential
by tortuga - 03/28/24 05:57 PM
Portable generator question
by Steve Miller - 03/19/24 08:50 PM
Do we need grounding?
by NORCAL - 03/19/24 05:11 PM
240V only in a home and NEC?
by dsk - 03/19/24 06:33 AM
Cordless Tools: The Obvious Question
by renosteinke - 03/14/24 08:05 PM
New in the Gallery:
This is a new one
This is a new one
by timmp, September 24
Few pics I found
Few pics I found
by timmp, August 15
Who's Online Now
0 members (), 248 guests, and 16 robots.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate Thread
Page 2 of 3 1 2 3
master66 #164994 06/16/07 02:37 AM
Joined: Jun 2007
Posts: 50
H
Member
Silly me, I didn't see the discussion link until after I sent a PM. Oops!

Anyway, here's how I think it works:

The diode connected to the switch is the key. When the circuit to this diode is completed, the current flows across the diode and effectively bypasses the lamp, diode and capacitor due to the other diode being connected backwards in respect to the diode on the switch. Without the diode connected to the lamp, the light would glow dimly. With the diode blocking the other half of the AC waveform, the lamp will only see the 0.7V or so dropped across the diode, not nearly enough to light a 120V bulb.

The polarized cap is probably to prevent flicker. I don't think it would be wise to screw in a CFL into this contraption!

hardwareguy #165004 06/16/07 01:44 PM
Joined: Nov 2005
Posts: 827
Likes: 1
J
Member
The caps were optional. The diodes were mandatory.
Joe

master66 #165008 06/16/07 01:58 PM
Joined: Oct 2002
Posts: 482
Z
Member
That's easy. It's magic...

Seriously though, in my head I can make it work if the switches are DPDT and configuired in sort of a "three-way" set up, but each switch would affect the other switch. Let me put it to paper...

Zapped #165010 06/16/07 02:15 PM
Joined: Nov 2005
Posts: 827
Likes: 1
J
Member

JoeTestingEngr #165015 06/16/07 03:20 PM
Joined: Oct 2002
Posts: 482
Z
Member
That was my next guess. The question throws you off if you're thinking in AC terms.

The Capacitors seem needless though. Lamps don't usually require much supply smoothing, unless I'm missing their intended purpose in the circuit?

Zapped #165016 06/16/07 03:21 PM
Joined: Oct 2002
Posts: 482
Z
Member
Oops, I didn't read back. The capacitors are in fact optional.

Zapped #165021 06/16/07 04:15 PM
Joined: Jun 2007
Posts: 50
H
Member
Not only are they optional, but I think they are there solely to throw you off.

I took another look and each lamp receives the full AC wave, so those polarized caps would go BOOM anyway. laugh

It might be CFL safe after all.

hardwareguy #165025 06/16/07 05:02 PM
Joined: Nov 2005
Posts: 827
Likes: 1
J
Member
You probably ought to take a third look at it HWG. I didn't put the caps in there to blow up or throw off, but to smooth out. If you still can't make sense of it, say pretty please with silicon on top, and I'll draw it up a little more clearly.
Joe

JoeTestingEngr #165030 06/16/07 08:07 PM
Joined: Jun 2007
Posts: 50
H
Member
Yup.... sure enough, the cap would work just fine. Man, this is a devious little puzzle.

Now I want to make one of these, put it in a nice Lexan box and confuse others. I have the pars laying around in the junk pile. I'll probably use neon bulbs instead of incandescents just too keep the contraption small.

I'm going to laugh if my professor puts this as a bonus question on a test in my Circuit Analysis & Design class.

I have seen some lamp designs that have a full wave rectifier and cap to reduce flicker but I honestly haven't had a noticeable flicker issue with incandescent lamps. The filament never has time to cool durning the tiny amount of time the voltage drops to zero in the sine wave.

How is it possible that a little circuit like this is so hard to understand? It's probably because I have never seen anything so weird! Is this a purely theoretical circuit or was a commercial design based on it?

hardwareguy #165032 06/16/07 09:01 PM
Joined: Feb 2002
Posts: 183
N
Member
The neons may give it away - only one electrode will glow, so people will know that there are diodes involved.

Page 2 of 3 1 2 3

Link Copied to Clipboard
Powered by UBB.threads™ PHP Forum Software 7.7.5