Step-by-Step DIY Rectifier Instructions

[Pilotgeek]

Want to charge a battery off your white wire, or just want to efficiently run some LED's directly? This circuit will take the alternating current from "the white wire", and turn it into the sweet, delicious direct current that batteries and LEDs love so much. All the parts are available from radioshack, and cost less than $8, provided you already have a soldering iron and other such tools.

First off, this is only a rectifier, not a regulator. What this means, is that the DC current is not guaranteed to be a specific voltage, and will vary a bit depending on the rpms of the engine. However, I have not needed to provide a regulator in my circuits as it seems to stay withing a fairly stable 5-9v. I've seen a few wild claims of 20+ volt spikes on other people's posts, but that may have been measured without any sort of load or stabilizing capacitors. When you measure voltage, always make sure you have a load. This is why I included resistors built into the circuit. It provides a guaranteed load, and helps keep the voltage spikes a little bit lower.

Lastly, the way I use my rectifier is without a battery, wired directly into a 4.5v LED flashlight, and a 3v LED bicycle tail light. Neither of them have any problem running at these voltages, and the total power used is only 1/4 watt. However, don't blame me if you end up burning out an LED =P. A good 6v battery will have no problems with these voltages.

These are all the parts you will need:

2- 1Watt resistors 10 ohm
2- 1000uf capacitors (16 volts MINIMAL). I used 35v.
1- 50v Full-Wave bridge rectifier

 

[Pilotgeek]

Step 1: Take the rectifier, and add a dab of superglue or other adhesive to the center of it. Place one of the capacitors on the glue, and allow time to try. Take note of the polarity. Make sure that the side of the capacitor with the black stripe is near the negative side of the rectifier, as shown. The rectifier is marked with a + and - on the outside edges. The 2 center pins are for the AC input.

 

[Pilotgeek]

Step 2: Bend the pins as shown, and then solder the connections highlighted in red. Snip off any excess wire. Repeat these steps with the second capacitor, gluing it to the other side and this time bending the capacitor's leads up to meet the existing connections. Once again, be sure the polarity of the capacitor is correct. Solder the second capacitor.

 

[Pilotgeek]

Step 3: Now we will add the resistors. Superglue the resistors to the sides of the capacitors as shown. Bend the leads around the existing connections, and snip off any excess material. Once again, solder in the red highlighted area to connect the resistors to the circuit. The orientation of the resistors does not matter, as resistors do not have polarity.

 

[Pilotgeek]

Step 4: This is the final step. Cut the resistor leads to length, and solder wires to them. Next, cut and solder the two leads coming out of the rectifier. I highly recommend using heat-shrink tubing.

And that's it! The pair of wires that are coming off of the resistors are DC output, and the pair of wires that are going directly to the rectifier are the AC input.

On the DC side, the negative wire is the one connected near the black stripe of the capacitor, and the positive is the one on the other side.

On the AC side, connect the white wire to either of the input wires, and make a ground wire that goes from somewhere on the engine to the other input wire.

 

[decoherence]

wow! you write & photograph the kama sutra of electronics.
yea. go ahead & scroll back up & it will make more sense. lol

i'm looking to use this ménage à trois for my bike.
i also have a headlight that uses 4.5v & a rear that uses 3v
before i saw this i was making a wiring harness.
i wonder if i can get that rectifier @ radio shack.

 

[Pilotgeek]

I picked my rectifier up at RadioShack. All parts here are available from radioshack, for convenience. My prototype though was entirely parts from an old PC power supply.

Kama sutra of electronics. lol.

 

[decoherence]

i got all of it @ radioshack.
i happy because a few month ago radio shack asked what they would like radio shack to change.
well, it worked. they are more like old school R.S.
i like it.

i put everything together & now i need to get more connectors for trailers for my harness.

then i will hook up my multi meter to see if i need to adjust.
even though it will not me under load.
hmmm i might try quick tying my multi to the handles to see it under load.

thank you for inspiring to solder again. it has been about 18 years. watching the solder being drawn into the connection feels good.

i would love to follow more of your guides.

 

[djstugots]

Thanks for the great post. Just out of curiosity, have you burned out any LED's with this (as it is running over your LED voltage thresholds)? Did you wire your lights in series or parallel? Did you use any limiting resistors in line with your LEDs?

 

[rohmell]

For anyone interested, the schematic is:

 

[Pilotgeek]

Thank you rohmell for the schematic.

I have not burned out any LEDs yet with this setup. I was concerned that I would, but they all seem to be within spec (not overbright or overheating). My headlight is a single 1/4 watt LED with integrated heatsink, and it seems very tolerant to any variations in voltage. It has no additional resistors.

My rear light is a Bell bicycle taillight, which appears to use a microcontroller to supply the LEDs with a pwm signal to limit current without resistors. I wired into the battery compartment. Again, this setup appears fine, though if I were to wire up a few red LEDs directly, I would first test using an additional 47ohm-220ohm resistor for each LED, depending on what brightness I wanted.

I actually am now using a 470 ohm resistor on my tail light, which reduces brightness a fair amount. My rear brakes have a switch which bypasses the 470 ohm resistor to make the tail lights fully light up, as a brake light.

 

[bishop letov]

Thanks for the Info...

Was looking to do this to my Own setup..

Keep the ideas flowing..

 

[impression]

For anyone interested, the schematic is:

NICE. I don't think i have a white wire on my engine, but i'll check. I might be able to incorporate this rectifier with the plans i have for a voltage regulator to keep it @ 5v or 6v to run LED's

 

[Pilotgeek]

If you can, get a switching regulator. A linear regulator will require a heatsink, and will waste the little power these engines put out.

 

[impression]

If you can, get a switching regulator. A linear regulator will require a heatsink, and will waste the little power these engines put out.

how much power in amps do you think these engines make >?

apparently they sit between 4-10v depending on the engine revs/min

if i can get 3amp @ 5v or 6v i will be happy

 

[Pilotgeek]

They produce a max of about 3 watts, so 3 amps is doubtful. What do you need that much power for?

 

[GearNut]

The white wire puts out 6 volts, 3 watts, 1 amp maximum under a load.
(Some cannot even do that good.)
If you try to make it power anything higher it will kill the signal to the CDI box and result in a no spark issue.

If you simply measure the voltage unloaded you can typically read anywhere from 10 to 14
volts. That unfortunately is not what it is capable of sustaining under a load.

 

[hotbug1776]

Question about the capacitors... 3300uf 16v ok? I can go get the 1000uf 35v and get the 10 1w resistors if needed. I have a 6v battery from an emergency light for head, brake, and signals.

I pulled a rectifier from a PC power supply, and have the needed resistors and the 3300uf 16v caps from said power supply.

Also, the regulator mentioned in this post... any chance of a tutorial on it as well, I'd be interested in learning how to build one of those as well.

 

[Pilotgeek]

3300uf 16v capacitors are fine, and would probably actually work better. I don't see the circuit going above 16v and the 1000uf are really more of a minimum requirement.

 

[hotbug1776]

Ok, next question... Do I need the resistors if I use the 6v battery I just scored for free from the scrap pile at work... its a 6v SLA.