Is there a red LED with similar characteristics to the other colors so that increasing the current will not result in the increase in red output relative to the rest? I brought all current contributors into the address in the event we move off list. I am also collecting into a single file by filtering my mail.
73, Bill K9YEQ -----Original Message----- Tom: Most of this has already been covered to some degree, but let me try to summarize. I got from Digi-Key some of the green LEDs from the same mfr (Avago) as the red ones provided with the W1 kit. Yellow and amber / orange are also mf'd by Avago but are not available in reasonable quantities (min order of over 3000 each), so I got some yellow and amber mf'd by Lumex with similar characteristics. (part numbers etc are in one of my prior posts). I installed green for D16, D17 & D18 (SWR of 1.1, 1.2 &1.3), yellow for D19 & D20 (SWR of 1.5 & 1.7) and amber for D21 (SWR of 2.0). When installed on the W1, all of the new colours are significantly dimmer than the red - depending on ambient lighting level ranging from very dim to visible. In the W1, the current in the LEDs is approx 1.5 ma per LED (calculated as [5V - 2V (the voltage drop across the LED)] / 2k) and it is switched on and off to each pair of LEDs by the microprocessor and back and forth from POWER and SWR by Q3 & Q4 (2N7000s). Using some of the extra LEDs, I hooked up one each of red, green, yellow and amber to a power supply set for 3 volts with a resistor substitution box and found that at 1.5 ma the brightness was as when installed in the W1. To get the brightness of the new colours up to a reasonable level took approx 6 to 7 ma and the red ones continued to be brighter than the other colours. (Note that the Luminous Intensity for the Avago LEDs is spec'd at a fwd current of 20 ma and this design is using fwd currents significantly less than that. (Lumex devices have similar spec's). The solution seems to be to reduce the value used for the resistor pack keeping in mind that the "reds" will always be brighter than the other colours because of the different fwd current vs luminosity curves for the different colours at this low current. With the given circuit layout, it is not possible to use different value resistors for each colour of LED because they are driven in pairs and then switched back and forth from POWER to SWR by Q3 & Q4. Note that RP2A serves to provide the current for both D6 (FWD Pwr of 1.5W) and D16 (SWR of 1.1:1) and so on. I'm going to continue looking for a different value of resistor pack to increase the visibility of the new colours without compromising the other aspects of the design - power dissipation in U3, battery life etc. Hope this helps. 73 Doug, VE3MV ----- Original Message ----- > I'm in the process of building the W1 and have substituted the colored LED's > on the SWR readout as has been discussed. > > I really haven't been following this thread closely and I haven't finished > the W1 build yet so this may have already been covered. > > I include myself when I say that it seems that everyone seems to be > replacing SOME of the red LED's with the green, amber and yellow jobbies. > And we seem to be using the red LEDs that came with the W1. > > Has anyone replaced ALL of the LEDs, including the RED ones. Wouldn't using > all now LED's from the same manufacturer, and specs give the desired results > of consistent brightness? > > Again, I didn't do this because I wasn't aware of the issue when started, > but the LEDs I got from Mouser were relatively inexpensive (about $0.15 > each) so this might have been an easier fix. > > Perhaps this had previously been covered. > > Just a thought > > Tom > WB2QDG > K2 1103 > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
