Which LED's to use in Cateye TL-LD130 Mod.

[ia02]

Hey everybody. New to all this so please forgive me if I ask fairly amateurish questions.

I'm looking to upgrade the LED's in my old Cateye TL-LD130 (just for a fun project and good backup light). This light has three rather dim 5mm Red LED's stock with places to add two more led's. The Tl-LD150 is exactly that, the same light with 5 LEDs instead of three. The problem is that all the 5mm led's that I am finding have forward voltage requirements of about 2v. My DMM tells me that I have only 1.5v at each of the sockets on the board of this light. It uses two AAA batteries so I assume they are wired in parallel.

I know this has been done many times before (see: http://www.inkhorn.net/site/log/Entries/2009/2/24_CatEye_TL-LD130_to_TL-LD150_mod.html ). Which led's should I use? Will a standard approx 2 volt red led light on only 1.5v or does this light use a strange special 1.5v led?

I figure i'll use the brightest 5mm red's I can get my hands on (that will actually work). I'm thinking of using one of these:

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=220443231344&_trkparms=tab=Watching

or

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&ssPageName=STRK:MEWAX:IT&item=350083964978


Let me know if you think these will work or if you have better suggestions on led's. Anything else I'm missing? Thanks in advance!!!


P.S. on a side note, cateye sells a "front marker" light that is essentially the same light with a white lens and white leds. How do they illuminate white leds on this voltage? maybe there's a resistor in place on the rear lights that is absent in these? any ideas?

 

[Steve K]

Hey everybody. New to all this so please forgive me if I ask fairly amateurish questions.

I'm looking to upgrade the LED's in my old Cateye TL-LD130 (just for a fun project and good backup light). This light has three rather dim 5mm Red LED's stock with places to add two more led's. The Tl-LD150 is exactly that, the same light with 5 LEDs instead of three. The problem is that all the 5mm led's that I am finding have forward voltage requirements of about 2v. My DMM tells me that I have only 1.5v at each of the sockets on the board of this light. It uses two AAA batteries so I assume they are wired in parallel.

how are you measuring the forward voltage at the leds? Is this with the light flashing? If so, the DMM might not be responding quickly enough to the pulsed voltage. You might verify how the batteries are wired.... check from the negative terminal of one to the positive terminal of the other. If it is zero, that means that those two terminals are wired together, so check the other terminals. If it is 1.5v, then they are indeed wired in parallel. If 3v, then they are in series.

Let me know if you think these will work or if you have better suggestions on led's. Anything else I'm missing? Thanks in advance!!!

I've been using some Kingbright red leds from Mouser.com, but they are relatively old technology. On the plus side, I can vouch for their quality and reliability, which is sometimes lacking in the leds purchased from ebay.

P.S. on a side note, cateye sells a "front marker" light that is essentially the same light with a white lens and white leds. How do they illuminate white leds on this voltage? maybe there's a resistor in place on the rear lights that is absent in these? any ideas?

Some white leds will light up with 3v, but are not as bright as with a higher voltage. I've got a little drop-in led for a Mag-lite that is like this. It is possible that Cateye uses a little boost converter too, especially if it is a recent design. I had a cheap little led flashlight that ran off of 1 AA battery that used a little boost converter, Cateye might do the same.

regards,
Steve K.

 

[ia02]

how are you measuring the forward voltage at the leds? Is this with the light flashing? If so, the DMM might not be responding quickly enough to the pulsed voltage. You might verify how the batteries are wired.... check from the negative terminal of one to the positive terminal of the other. If it is zero, that means that those two terminals are wired together, so check the other terminals. If it is 1.5v, then they are indeed wired in parallel. If 3v, then they are in series.

I checked the voltage at the open sockets where the new led's will go with the light on constant. not flashing. Unless there is a flaw in this technique I'm pretty sure it is indeed only 1.5v to each LED.

I'll use your method to check on the parallel/series setup of the batteries and report back.

Thanks Steve....

 

[ia02]

You might verify how the batteries are wired.... check from the negative terminal of one to the positive terminal of the other. If it is zero, that means that those two terminals are wired together, so check the other terminals. If it is 1.5v, then they are indeed wired in parallel. If 3v, then they are in series.

Steve, just got this checked out. It does indeed have 3v at the batteries, so they are wired in series. But as I had found before, 1.5V at the solder points on the PCB. Maybe I'll take some pictures of the board, i'm sure there are some resistors or something i don't recognize that could get me back to the full 3V.

So I guess for now its back to my other question: Anybody know of any reasonably bright leds that run on 1.5V. Hopefully something that turns out to be brighter than the current leds (i guess thats the whole point of this exercise...).


-ian

 

[Steve K]

I checked the voltage at the open sockets where the new led's will go with the light on constant. not flashing. Unless there is a flaw in this technique I'm pretty sure it is indeed only 1.5v to each LED.

I'll use your method to check on the parallel/series setup of the batteries and report back.

Thanks Steve....

weird....
my only thought is that perhaps the "constant" mode is really strobed, but strobed fast enough that you don't notice it. This is done on car led taillights. If you scan your eyes past the leds quickly, you can see the on-off pattern. If the Cateye light is on for 1ms and off for 1ms, then a DMM would interpret the voltage as being half of what it actually is during the on time. This is where an oscilloscope would be extremely handy.

Or you could ask Cateye themselves how they do it....

regards,
Steve K.

 

[ia02]

weird....
my only thought is that perhaps the "constant" mode is really strobed, but strobed fast enough that you don't notice it. This is done on car led taillights. If you scan your eyes past the leds quickly, you can see the on-off pattern. If the Cateye light is on for 1ms and off for 1ms, then a DMM would interpret the voltage as being half of what it actually is during the on time. This is where an oscilloscope would be extremely handy.

Or you could ask Cateye themselves how they do it....

regards,
Steve K.

Good call. I was also thinking i could go down to REI and and see if i can visually see a difference between the white (front) and red (rear) versions of this light. I'm thinking that maybe they could get a red led to run on 1.5v but it doesn't seem possible to run white leds on 1.5v. Maybe there is a resistor present in the red version that is not present in the white. Could be as simple as removing/jumping that resistor to get my full voltage.

In the end probably not worth it when I can get a nice little Planet Bike Superflash for like $30. I guess I just like to mess with things. If it's not broke: FIX IT!

cheers...

-Ian