On Tuesday, December 10, 2013 4:54:21 PM UTC-5, Tony Hwang wrote:
jamesgang wrote:

On Tuesday, December 10, 2013 2:55:12 PM UTC-5, Tony Hwang wrote:

jamesgang wrote:



On Tuesday, December 10, 2013 1:24:28 PM UTC-5, Jennifer Murphy wrote:



On Tue, 10 Dec 2013 09:54:20 -0800 (PST), "







wrote:















On Tuesday, December 10, 2013 11:30:17 AM UTC-5, Jennifer Murphy wrote:







On Tue, 10 Dec 2013 05:45:31 -0800 (PST), "















wrote:































If the box has no neutral, then there is no code compliant







way to make the switch that requires it work. The issue is







that a programmable switch needs to be powered somehow. That







could be by a battery, through the hot and neutral, or by







using the load circuit. The latter is why the other switch







has a minimum load of 25W. Without some kind of minimal load







for a small current to flow through and power the switch even







when it's off, it would have no power. That small current flows







through the bulb when off and it's enough for thw switch, but







so tiny it won't light the bulb at all.















The minimum it said it needed was actually 40W.















Does the switch really draw 40W for its own use?















No, it draws negligible amount of power. If it drew







40W the box would over heat. It's just that with no







neutral, the switch winds up getting it's power in







series with whatever the load is. With too small of a







load, the switch can't get the necessary voltage/current







that it needs.















If the switch obnly needs a fraction of a watt to operate, why does it







say that the load must be at least 40W? Why couldn't it get ebnough







power with a 5W bulb as the load. 5W is much larger than a fraction of a







watt.















I should have paid closer attention in freshman physics.







The switch is in series with the load, in this case a light bulb. So if you only have a 5 watt bulb the current flow would be too low to generate the needed voltage at the switch. Read about resistors in series if you are really interested in the physics and consider one of the resistors the switch and the other, the light bulb.







Hi,



Sounds like it is SS type switch like SCR. Without proper load creating



enough current flow the gate can't trigger to make the



switching device close(conduct. Think in terms of electronics, not



electric/mechanical. Read up on things like SCR, TRIAC, DIAC, DIODES,



opto electric Darlington switch, etc. On the other hand some of those



kinda switches always have residual current flow even if off state.



Use that switch on CFL light, you will see it just dims when turned off.



That's not the issue.



The timer uses the line through the load to operate it's clock because it has no neutral. If the load is missing or not enough the clock doesn't work properly. 5 watts is plenty of load for a scr or triac.



Hmm,

So, I = P/E 5/120~~ 42 mA. Not much of a current.

It's plenty of current to run the clock/timer/lcd electronics in the
programmable timer. How much current does it take to run
a digital watch?




If there is no

neutral Is it open circuit? I don't get it.

(switch)(load) where does this line end up? No neutral?

When the switch is off, it relies on the path through the load,
to the neutral, to complete the circuit. That's why the load has
to be at least 40W, or whatever the number was.