Again, it was the LED board only.. No other parts other than the 14 white LED's in series.
-----Original Message----- From: EV <ev-boun...@lists.evdl.org> On Behalf Of Lee Hart via EV Sent: Friday, July 27, 2018 1:43 PM To: Electric Vehicle Discussion List <ev@lists.evdl.org> Cc: Lee Hart <leeah...@earthlink.net> Subject: Re: [EVDL] Reduce EV: Charging load on the grid ... LEDs Robert Bruninga via EV wrote: > The 60W equivalent I just took apart had a full 14 LEDs in series but > still used a PWM controller. > > It took 80 volts DC to get the LED's to their proper brilliance. So > just a small resistor will do. Right. And a rectifier. :-) 80/120v means a simple series resistor would make it 67% effient. Not bad. 40v at 60ma is 2.4 watts of waste heat. > What was interesting was that 3 came on at around 15 volts, then more > and more came on as the voltage was raised. And they shifted back and > forth at various levels until they were all on. My guess is that there is more to the circuit than may appear. The flashing could be a side effect of the PWM circuit's "brownout" characteristics. It's also possible that there are other parts inside the LED package itself, too. Some are designed for applications like 5v indicators or 12v car lights, and have their own internal regulator or limiter. All these LED lights are made in China. They will use whatever part falls to hand this week, regardless of its specs or source. > PS, this divides out to be about 5.7 volts per LED. Much higher than > the 2.8v mentioned? Was that actually measured at the LED? Or just 80v at the PWM input, divided by 14 LEDs? It is likely that the PWM itself has a considerable voltage drop, so this won't properly estimate the LED voltage. It's also possible that each LED actually has more than one chip inside. The 2.8v I used in my example was for the red LEDs inside a cheap car tail light. That's actually rather high for red -- typical red LEDs are usually 1.6-1.8v. But they were driving these red LEDs at excessive currents; about 100ma, when the part's data sheet says 60ma absolute maximum. (This is unfortunately a common practice). White LED voltages are generally higher; in the 3.x volt range. -- Problems that go away by themselves will be back with friends. Lee Hart, 814 8th Ave N, Sartell MN 56377, www.sunrise-ev.com _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub http://lists.evdl.org/listinfo.cgi/ev-evdl.org Please discuss EV drag racing at NEDRA (http://groups.yahoo.com/group/NEDRA) _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub http://lists.evdl.org/listinfo.cgi/ev-evdl.org Please discuss EV drag racing at NEDRA (http://groups.yahoo.com/group/NEDRA)
