Dec 1, 2013 #1 F fences Junior Member level 3 Joined Feb 7, 2011 Messages 25 Helped 0 Reputation 0 Reaction score 0 Trophy points 1,281 Activity points 1,453 hello i used this circuit for light on LED. R = 82k - 250mw D = 1N4007 Is this circuit safe for work long time? is there any better idea? Thanks.
hello i used this circuit for light on LED. R = 82k - 250mw D = 1N4007 Is this circuit safe for work long time? is there any better idea? Thanks.
Dec 1, 2013 #2 G godfreyl Advanced Member level 5 Joined Apr 18, 2012 Messages 1,974 Helped 632 Reputation 1,266 Reaction score 621 Trophy points 1,393 Activity points 12,772 If your AC is 240V then the resistor will burn. The power dissipation will be 240V*240V/82K=700mW, but your resistor is only rated for 250mW. If your AC is 120V then it should be OK. The circuit isn't safe though. You may be electrocuted if you touch any part of it while it is connected to mains.
If your AC is 240V then the resistor will burn. The power dissipation will be 240V*240V/82K=700mW, but your resistor is only rated for 250mW. If your AC is 120V then it should be OK. The circuit isn't safe though. You may be electrocuted if you touch any part of it while it is connected to mains.
Dec 1, 2013 #3 F fences Junior Member level 3 Joined Feb 7, 2011 Messages 25 Helped 0 Reputation 0 Reaction score 0 Trophy points 1,281 Activity points 1,453 thanks, what is your idea for a safe and simple board for this?
Dec 1, 2013 #4 G godfreyl Advanced Member level 5 Joined Apr 18, 2012 Messages 1,974 Helped 632 Reputation 1,266 Reaction score 621 Trophy points 1,393 Activity points 12,772 If you use a 2W resistor instead of a 250mW resistor, the circuit will work for a long time. That is the simplest way. If you want it to be safe then it must be inside an enclosure so nobody can touch any of the connections.
If you use a 2W resistor instead of a 250mW resistor, the circuit will work for a long time. That is the simplest way. If you want it to be safe then it must be inside an enclosure so nobody can touch any of the connections.