icube2
Electrical
- Feb 23, 2011
- 1
Hi guys,
I made a circuit for a Multivolt LED lamp. The circuit works for 24V dc but doesn’t work for 120 V ac. When I supply 120 V ac, the R4, R5 and R6 resistors on the attached circuit diagram gets really hot. I thought my calculations were correct but apparently not.
This is how I calculated the values for the resistors.
For 24V dc:
R1 = (24 – 14) / 0.01 => 1K
R1 = R2 = R3 = 1 K
For 120V ac:
Voltage drop on R4, R5 and R6 is (120 - 24) = 96V
Total current 30mA (3*0.01A)
Equivalent resistor (96 / 0.03) = 3200 ohm (10K || 10K || 10K)
Power dissipation on equivalent resistor (96 * 96) / 3300 = 2.8 W (about 0,9W each resistor)
But I am using a 2W resistor.
Any ideas what can I do to make it better?
Thanks,
I made a circuit for a Multivolt LED lamp. The circuit works for 24V dc but doesn’t work for 120 V ac. When I supply 120 V ac, the R4, R5 and R6 resistors on the attached circuit diagram gets really hot. I thought my calculations were correct but apparently not.
This is how I calculated the values for the resistors.
For 24V dc:
R1 = (24 – 14) / 0.01 => 1K
R1 = R2 = R3 = 1 K
For 120V ac:
Voltage drop on R4, R5 and R6 is (120 - 24) = 96V
Total current 30mA (3*0.01A)
Equivalent resistor (96 / 0.03) = 3200 ohm (10K || 10K || 10K)
Power dissipation on equivalent resistor (96 * 96) / 3300 = 2.8 W (about 0,9W each resistor)
But I am using a 2W resistor.
Any ideas what can I do to make it better?
Thanks,
