mxracer700
New Member
Hi All,
Thanks in advance to anyone who can shed some light here.
Building a simple circuit to add LED headlights a child's battery ride on car.
Each headlight has 3 white 10mm water clear LED wired in series. (20,000mcd,4.0v, 20ma) each for a combined draw of 12v. There is parallel wiring between the left and right headlight assemblies and then it's wired from the left one back to the battery and switch. Using an online LED calculator I added the suggested 1 ohm resistor to the neg lead off the left assembly LED's only as a test. It lasted seconds and blew all 3 LED. Yet the right headlight assembly which has been connected directly to power (no resistor) for a while has not failed yet. After the first set on the left blew and because the other set with no resistor did not, I replaced the 3 dead LED and almost immediately they blew again while the right is still running fine. To clarify the power comes to the left side assembly first and then parallels over the to the right and ends there.
1. It is perhaps my false understanding that if a string of series LED matches the voltage (3 x 4v =12v) a resistor is not required as long as the power source is constant. T or F?
2. If that is False then why did the setup blow with the suggested resistor in place and why not the other side with no resistor?
3. Does it matter if the resistor is added to the pos or neg side of LED's both single or series?
Any info on this would be huge help, scrambling to get this project ready for Santa to deliver.
Cheers, MXR.
Thanks in advance to anyone who can shed some light here.
Building a simple circuit to add LED headlights a child's battery ride on car.
Each headlight has 3 white 10mm water clear LED wired in series. (20,000mcd,4.0v, 20ma) each for a combined draw of 12v. There is parallel wiring between the left and right headlight assemblies and then it's wired from the left one back to the battery and switch. Using an online LED calculator I added the suggested 1 ohm resistor to the neg lead off the left assembly LED's only as a test. It lasted seconds and blew all 3 LED. Yet the right headlight assembly which has been connected directly to power (no resistor) for a while has not failed yet. After the first set on the left blew and because the other set with no resistor did not, I replaced the 3 dead LED and almost immediately they blew again while the right is still running fine. To clarify the power comes to the left side assembly first and then parallels over the to the right and ends there.
1. It is perhaps my false understanding that if a string of series LED matches the voltage (3 x 4v =12v) a resistor is not required as long as the power source is constant. T or F?
2. If that is False then why did the setup blow with the suggested resistor in place and why not the other side with no resistor?
3. Does it matter if the resistor is added to the pos or neg side of LED's both single or series?
Any info on this would be huge help, scrambling to get this project ready for Santa to deliver.
Cheers, MXR.