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Under-pedal hover-glow lights mod


Czestnut

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Back in my day, guys added neon lights underneath their cars to make them look they are floating on lights.  So today I am waiting for the sun to go down so I can try out my new mod.

First test was using those glow-shoelaces you get at dollar or party stores.  They are cheap and batteries included.  I simply scotch-taped them to the bottom, and I got some dimly-lit effect under my feet.  Laces started dimming after an hour, and they are not going to last for 3,tops.

 

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So I scrapped those, and recently I ordered these LED Halo lights off eBay in deep blue.  My only regret was getting them in the smallest 40mm. They are meant for cars, so that means they are set for 12v.  So this is how one looks like when you get it.  It wasn't very bright when I connected it to my intended 9v battery idea.  I prayed that the LED halo could operate at a lower voltage, and that black thing was just a resistor.

 

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I snipped it off and...

EUREKA!

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So here's the intended circuit, and now to connect it to my TG-T3.  Take note of the wire colors.  It won't work if you mistake the polarities.

IMG_1423.JPG

 

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Fortunately black electrical tape hides the wires running across the body.  I'll put up a more secure battery holder another time.  Be sure to carefully run the wires under the pedal away from where the wires could be pinched when pedals down.  It looks pretty sick with the lights out in the room.  Now I have to wait until the sun goes down, and take pics of the final effect.

Image3.jpg

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Success!  So many WTF's riding around in the hood.

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Cars stoppin', girls wavin'...

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14 hours ago, Czestnut said:

I prayed that the LED halo could operate at a lower voltage, and that black thing was just a resistor.

Looks more like a capacitor to me... if that was the front resistor, removing it and powering the leds (assuming the 9V was enough voltage, like it was) you would have burned the leds ;)

For "longer" term usage (ie. not having to replace batteries), you could use a step-down converter that can take the battery voltage (up to around 68V at least) and drop it to 12V (like this one: http://www.aliexpress.com/item/Step-down-Transformer-Electric-Bike-DC-Converter-Adapter-36V-48V-72V-TO-12V-10A/32358226204.html ). Assuming you could fit that somewhere inside the wheel, you could then power the lights directly from battery, but probably need to add a switch somewhere, otherwise they will always be on and drain your battery :P.

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50 minutes ago, Cloud said:

Will these lights work on 3v? Or wil, they be too dim?

It depends on the leds and how they're put in the circuit. Leds have a forward voltage from around 2V (red) to over 3V (blue/green/white):

LED_FWV.jpg

If there are multiple leds in series in those rings, you need enough voltage to overcome the sum of all the forward voltages. If they're in parallel, then you only need to overcome the forward voltage of a single one.

The front resistor is what limits the current to the led. It's fairly straightforward to calculate, when you know the forward voltage drop of the led (at least roughly, no need to know it down to millivolts or such), what your input voltage is and how much current (ie. how bright) you want the led to burn.

As an example, let's say you want to light a red led with 5V input voltage. The typical forward voltage of a red led is around 2.2V. The front resistors must thus drop a voltage of:

Input voltage - led forward voltage = 5V - 2.2V = 2.8V

Now we know the voltage over the resistor, and the current we want is 20mA (for example). That's 0.02A. To allow 20mA of current over a resistor that must drop 2.8V of voltage, the resistor must be:

R = U/I   R = 2.8V / 0.02A = 140 ohms.

I don't think that's a standard resistance, so pick the closest one available: 150 ohms.

To be on the safe side, it could also be calculated using the minimum forward voltage (as it will cause more voltage drop over the resistor), as the forward voltages can vary between different leds of same color (like the chart above shows, the forward voltage of a red led for example will be somewhere between 1.7-2.4V, but is typically around 2.2V).

 

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2 hours ago, esaj said:

Looks more like a capacitor to me... if that was the front resistor, removing it and powering the leds (assuming the 9V was enough voltage, like it was) you would have burned the leds ;)

For "longer" term usage (ie. not having to replace batteries), you could use a step-down converter that can take the battery voltage (up to around 68V at least) and drop it to 12V (like this one: http://www.aliexpress.com/item/Step-down-Transformer-Electric-Bike-DC-Converter-Adapter-36V-48V-72V-TO-12V-10A/32358226204.html ). Assuming you could fit that somewhere inside the wheel, you could then power the lights directly from battery, but probably need to add a switch somewhere, otherwise they will always be on and drain your battery :P.

It's shape looks like a capacitor, but indeed a resistor they placed in a shell and filed with black glue gun material by the looks of it. It definitely reduced power to the LEDs, so after removing it, I started with a simple AA battery then to a 6v pack, and that gave me peace of mind to go my intended 9v. 

9v batteries are dirt cheap, aren't heavy and hide well on my ride. I didn't want to make it any more complicated. 

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7 hours ago, Cloud said:

Will these lights work on 3v? Or wil, they be too dim?

1.5 was very dim, 6v was better, 9 was best.  I don't know if I am over-volting it, but hey, it wasn't an expensive mod.

9 hours ago, dmethvin said:

Nice mod! How long does the battery last? 

I just did yesterday, so I believe it will take time.  It's a generic alkaline 9V battery, and it hasn't dimmed at all after 2hrs of riding last night.

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You should, just for test purposes, get a 12 v source and with the supplied resistor, measure the voltage across LEDs and the take a current reading, then you will know what would be safe and figure what new resistor is needed at 9 volts...if needed...

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I do have a multimeter and should have done that earlier, but it's all wired up nicely to me wheel now.

 

p.s. for those who asked, 6hrs on the 9v battery and still full brightness.

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On 18/06/2016 at 5:12 PM, esaj said:

 step-down converter that can take the battery voltage (up to around 68V at least) and drop it to 12V (like this one: http://www.aliexpress.com/item/Step-down-Transformer-Electric-Bike-DC-Converter-Adapter-36V-48V-72V-TO-12V-10A/32358226204.html ). 

Thanks for the link @esaj! A bit of OT but I'm currently in opposite situation looking for 12 to 58 - 70 (-ish) V step up converter.

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1 hour ago, HEC said:

Thanks for the link @esaj! A bit of OT but I'm currently in opposite situation looking for 12 to 58 - 70 (-ish) V step up converter.

I have one of these, but haven't tested it much (other than that it really does give out high voltage ;)):

http://www.aliexpress.com/item/High-Efficiency-95-DC-DC-600W-IN-12-60V-OUT-12-80V-Boost-Converter-Step-Up/32374850067.html

Actually, it went up to above 90V without load (just multimeter measuring voltage), after which I started to crank it down, as the capacitors on it were rated for 100V... :D

There was a mention in some other seller not to use it above 400W without extra cooling.

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2 hours ago, esaj said:

I have one of these, but haven't tested it much (other than that it really does give out high voltage ;)):

http://www.aliexpress.com/item/High-Efficiency-95-DC-DC-600W-IN-12-60V-OUT-12-80V-Boost-Converter-Step-Up/32374850067.html

That's spot on! Thanks again @esaj ;) I'd be fine even with some smaller one with less Watts / Amps and most of all smaller and lighter however those in general goes only to 30 something V on outputs so I guess I'll try this one. It claims to have fairly high eficiency a well which would be great for my application.

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4 minutes ago, HEC said:

That's spot on! Thanks again @esaj ;) I'd be fine even with some smaller one with less Watts / Amps and most of all smaller and lighter however those in general goes only to 30 something V on outputs so I guess I'll try this one. It claims to have fairly high eficiency a well which would be great for my application.

Search around Aliexpress, "step up converter" and "boost converter" are good search words. At a quick try found at least this (160W / 60V max):

http://www.aliexpress.com/item/DC-Boost-Converter-DC-8-40V-to-12-60V-10A-160W-Adjustable-Power-Supply-Module-DC/32624351102.html

In most cases you can tell the higher voltage ones just by the large coils vs. the up to 35V or so -models.

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26 minutes ago, Rehab1 said:

@esaj Your technical background never ceases to amaze me!

I still consider myself an amateur when it comes to electronics, but keep (slowly) improving. I still trip on the very basics a lot when designing my own circuits, though :D 

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  • 2 weeks later...

BTW, I got over 10 hours out of my first alkaline battery, until my rechargeable 9v Li-ion arrived from its long boat trip from China.  It could be double that I don't know, so I'm happy with the battery approach.

 

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