Adding an LED to a Weber MASS

[GBStratman]

This is kinda silly, but I think I think the THD hotplates look cool with the LED that lights up when power is being dumped. I don't use a hotplate, but I do have a Weber Mass Lite. I was thinking I could add an LED in series with a resistor across the mass motor to get the same effect. With a voltmeter I measured about 15VAC across the motor with the attenuator in line with the amp and speaker and playing reasonably hard. I would need another diode for the negative current. Do you think this would work?

[Bruce / Mission Amps]

This is kinda silly, but I think I think the THD hotplates look cool with the LED that lights up when power is being dumped. I don't use a hotplate, but I do have a Weber Mass Lite. I was thinking I could add an LED in series with a resistor across the mass motor to get the same effect. With a voltmeter I measured about 15VAC across the motor with the attenuator in line with the amp and speaker and playing reasonably hard. I would need another diode for the negative current. Do you think this would work?

Yes... it should work fine.
I don't think it will make a sonic difference but you might want to start with a bigger current limiting resistor then you think because an LED will to draw about 15ma to +20ma for good visual brightness.
If you decided 15ma is bright enough then it would be simple math ...
15v/.015a = 1000 ohms, 15v/.020a = 750 ohms.
.02a x 15v = .3w, but I'd use a one watter anyhow.
But the amp might actually make much more then only 15v with loud volume peaks so I'd start with something like 1500 ohms and work the resistor value until I was happy with the brightness and the lack of blowing the LED.
I don't think you need another diode as you are only making a half wave rectifier out of it.

[GBStratman]

Thanks. I figured I would need an inverse diode in parallel with the LED to prevent the LED from blowing from potentially high reverse voltage.

[Old Tele man]

...a parallel Zener diode could be added to "clamp" all power voltages which exceed any 'do not exceed' voltage.

[GBStratman]

...a parallel Zener diode could be added to "clamp" all power voltages which exceed any 'do not exceed' voltage.

Sorry, now I'm confused. A zener in parallel with the LED, or in parallel with the current limiting resistor + LED ? Would I need to add another dropping resistor as in a voltage regulating circuit?

[GBStratman]

Here is what I ended up doing. Seems to work fine.

[jeffro]

I am trying to add a check led to an old mxr 117 flange pedal, and I do not understand enough about circuit components. what do I add, where?