GD750 or NG750 for SSC P4

[digitaleos]

Which converter would give the longest regulated output for the Seoul running off of a single R123? Now as far as brightness, since they are both 750ma, they should both be the same brightness, right?

Chris

 

[LED Zeppelin]

They should be the same brightness in regulation, but on a full charge the NG will start in direct drive since the Vin > Vf. You'll probably be over 1000mA at first, and the NG will be noticeably brighter. It may or may not be adviseable depending on Vf, heatsinking, and your concern for lumen maintenance.

The GD will be in regulation from the start, and buck or boost depending on the cell voltage.

The GD is more efficient at 85-93% vs. 80-91%, so given that the NG starts out of regulation and overdrives the emitter, the longest regulated output will be the GD.

 

[digitaleos]

LZ, thanks for the response. Now I have another question, can a 2 stage switch be used with the GD converter? :thinking: What would be my best option for running the Seoul in the 750-917ma range with regulation and still be able to use a 2 stage switch? This would be a one cell configuration.

Chris

 

[LED Zeppelin]

2-stage will work with the GD, but you need much lower resistances.

With the GD and an RCR123, 10 ohms or less. If you plan on using a primary cell, 5 ohms or less.

 

[digitaleos]

LED Zeppelin, Thanks again. I will be mainly using a R123. I ordered a GD917 from the Shoppe along with a McE2s with the 5ohm resistor, any ideas on the lumen output on high and then low with the 5ohm resistor? This will be used with a McR27L-S reflector.

Chris

 

[LED Zeppelin]

Chris,

No idea other than it's going to be a very nice light!

I have a GD825 A19 XR-E, and with a 10 ohm resistor the low level is not quite as bright as an Arc AAA-P. The hi is very bright, maybe 100+ lumens.