DIY Night blades

[TheBum]

Originally Posted by mastmalang70

ohh thanks, so ,vf is a forward voltage
i need one with 3.7 volts any link
thanks again

Due to the semiconductor "stew" required for each color, I doubt you will find an LED in a color other than blue that will be able to take a straight 3.7-4.2V.

There's also the issue of the changing battery voltage as it discharges. It will start at 4.2V, so a 3.7V LED would be overloaded at first. It's possible the LED would survive for a while, but that extra voltage and the associated extra current is likely to gradually damage the LED until it fails. With a resistor, the LED can adjust its voltage and current as needed.

[mastmalang70]

i saw on the site they also sold resistors ,and in the begining of forum there is a calculator ,only want to know what type of resistor i need ?????? here is the link for different type on the site
thanks
http://www.rapidonline.com/Electroni...-Potentiometer

[TheBum]

Originally Posted by mastmalang70

i saw on the site they also sold resistors ,and in the begining of forum there is a calculator ,only want to know what type of resistor i need ?????? here is the link for different type on the site
thanks
http://www.rapidonline.com/Electroni...-Potentiometer

You'll undoubtedly want SMD (surface mount) resistors. I used 1206 sized SMDs on my blades because they were available locally at Fry's, but the 0805 ones, which are physically smaller, would work too.

[mastmalang70]

ok here are my findings please advise
1 , for 2.5 vf and 25ma ,calculator showed 68ohms 1/4w resistor
2 , for 3.8 vf and 25ma ,calculator showed 18ohms 1/4w resistor
for both if i use 4 smd's in parallel and with each smd a resistor

if i wana use different vf smd simply change the resistor ????

[TheBum]

Originally Posted by mastmalang70

ok here are my findings please advise
1 , for 2.5 vf and 25ma ,calculator showed 68ohms 1/4w resistor
2 , for 3.8 vf and 25ma ,calculator showed 18ohms 1/4w resistor
for both if i use 4 smd's in parallel and with each smd a resistor

Those resistor values look correct. The second one should ideally be 16 ohms, but 18 ohms is probably the closest available for sale. I would suggest looking around for a lower Vf blue LED though because when the battery voltage gets close to 3.8V, that LED will dim significantly and finally extinguish. The place where I got mine has blue LEDs with Vfs of 3.1-3.2V. In fact, I'm running those particular blue LEDs on the tops of my blades.

If you're running the same LEDs (color and part number) in parallel, you can treat them like one higher-powered LED and only use one resistor. In that case, you'd keep the voltage the same but multiply the current by the number of parallel LEDs when calculating the resistance. If doing so would unduly complicate the placement of the foil traces, it would be better to use one resistor per LED.

if i wana use different vf smd simply change the resistor ????

Yes.

[mastmalang70]

Originally Posted by TheBum

Those resistor values look correct. The second one should ideally be 16 ohms, but 18 ohms is probably the closest available for sale. I would suggest looking around for a lower Vf blue LED though because when the battery voltage gets close to 3.8V, that LED will dim significantly and finally extinguish. The place where I got mine has blue LEDs with Vfs of 3.1-3.2V. In fact, I'm running those particular blue LEDs on the tops of my blades.

If you're running the same LEDs (color and part number) in parallel, you can treat them like one higher-powered LED and only use one resistor. In that case, you'd keep the voltage the same but multiply the current by the number of parallel LEDs when calculating the resistance. If doing so would unduly complicate the placement of the foil traces, it would be better to use one resistor per LED.


Yes.

Thanks The Bum you are very wisely helpful,one more thing i need to know about resistors,
is carbon resistors are okay instead of using surfadce mount resistors because they come in a package of 5000 pieces ,too much for beginner project

[TheBum]

Originally Posted by mastmalang70

Thanks The Bum you are very wisely helpful,one more thing i need to know about resistors,
is carbon resistors are okay instead of using surfadce mount resistors because they come in a package of 5000 pieces ,too much for beginner project

You can, but they won't hug the surface of the blade as much. As long as you run them in a chordwise direction, you should be fine. Make sure they're 1/4W or smaller, mainly to keep the physical size at a minimum.

If you shop around, you should be able to find SMD resistors in much smaller quantities. For example, I know you can get them in single quantities at DigiKey. I don't know how much international shipping would be for you though.

[mastmalang70]

Originally Posted by TheBum

You can, but they won't hug the surface of the blade as much. As long as you run them in a chordwise direction, you should be fine. Make sure they're 1/4W or smaller, mainly to keep the physical size at a minimum.

If you shop around, you should be able to find SMD resistors in much smaller quantities. For example, I know you can get them in single quantities at DigiKey. I don't know how much international shipping would be for you though.

it doesnt worth it ,shipping is way way too much , even from UK on the order of 6 euro i have to pay 30 euro shipping ,only option of DHL i guess
thanks for great help,learn a alot

[TheBum]

One more thing: I'd recommend that you use a tiny bit of epoxy to adhere the resistors to the blades, since they are significantly larger than an SMD.

[TheHeliDude]

Do you guys CA the batteries down in addition to using heat shrink. While testing my battery flew out of the heat shrink. Im using the heat shrink kavic posted on this thread from amainhobbies. I'm wondering if I need to just apply the heat shrink better but I'll probably CA it to be safe.

Also, thanks for all the information on here guys. This has been easier than I thought.

[ChrisH]

I use double sided tape underneath my batteries, then shrinkwrap tightly. Never had a problem.

[TheBum]

Originally Posted by ChrisH

I use double sided tape underneath my batteries, then shrinkwrap tightly. Never had a problem.

Same here.

[Jonathan Ott]

Here's a spin up of my new DIY blades.

Jon

[badastinner]

Originally Posted by Jonathan Ott

Here's a spin up of my new DIY blades.

Jon

Nice!

[powerstroke01]

Oops

[Jonathan Ott]

I just did these blades last night, and threw a video on YT.