Hi all. I'm a total novice and just enjoying working through the fantastic resource material on the site. Meanwhile I'm trying to figure out how to build an LED circuit powered from a 110V 60Hz AC line. I found the attached schematic online but I'm stumped by the resister? Why is R1 in parallel with D1. Also the capacitor limits voltage but does it also serve to limit current? If someone could kindly give an explanation of what's happening in this circuit I would be very grateful. Thank you.

 

For safety reasons, the rules on this forum don't allow us to advise on the building of such things: they really are not safe, especially for beginners. I can't therefore tell you how to make one, but perhaps it would be OK to tell you a few general facts:

1. R1 is in parallel with the supply, not with D1. It serves to give a discharge path so the capacitor won't stay charged to give a shock hazard when the unit is disconnected.
2. The capacitor limits the current in the circuit, or at least it forms a major part of the circuit impedance that defines the current for a given AC input. Strictly, there is no definite current limit.

If you want to make a safe LED light, use a transformer. We can give you details on doing that.

 

Yes, mains-powered LED discussions are strictly forbidden according to the TOS of this site. You will be lucky if this thread does not get closed. I would highly recommend just using a wall wart, which is a step-down transformer, often with rectification and over-voltage protection built in already. That is the best way to do it, and it will be much safer.

 

I guess the reason this topic is forbidden, is that "building" and "testing" can be dangerous for anyone, and it certainly will be for beginners.

I'm not talking especially about THIS circuit but in general I do not agree that the circuits are not safe, once built and sealed into an appropriate casing. I think there is a distinction to be made. It's not the circuit that is unsafe, i.e. but its handling/testing.

Of course nobody in his right mind would test any non-mains isolated prototype on mains voltage.

In other words, start with something less dangerous.

 

This circuit is definitely not allowed according to the TOS:

6. Restricted topics. The following topics are regularly raised however are considered "off-topic" at all times and will result in Your thread being closed without question:

Any kind of over-unity devices and systems
Automotive modifications
Devices designed to electrocute or shock another person
LEDs to mains
Phone jammers
Rail guns and high-energy projectile devices
Transformer-less power supplies

 

Hello,

I am closing this thread as it violates AAC policy and/or safety issues.

Quote:
6. Restricted topics. The following topics are regularly raised however are considered “off-topic” at all times and will results in Your thread being closed without question:

• Any kind of over-unity devices and systems
• Automotive modifications
• Devices designed to electrocute or shock another person
• LEDs to mains
• Phone jammers
• Rail guns and high-energy projectile devices
• Transformer-less power supplies

This comes from our Tos:
Terms of Service

Bertus

 

Side comment, use a Wall Wart, a DC power supply that plugs into the AC outlet. This is safe, and will be allowed for discussion here.