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How to keep you lights off until the bike is running

26K views 64 replies 22 participants last post by  Nico 
#1 ·
Hi all,

Intro

Now I found a couple of threads on this, but they were a couple of years old and I wasn't much of a fan of the method they used, one was using the un-rectified output of the alternator to switch a relay, and another was a timer based solution.

My controller monitors the battery voltage to decide if the headlights should be on or not.
What I have based my design on is the fact that before the bike starts you have at most 12.5V in the system and once your running and charging the battery you have around 14V.
The aim is that by monitoring the battery voltage, when the circuit senses the voltage getting above a threshold value the headlights turn on, and then stay that way.

Parts List

Here is a parts list of what you will need to build this controller with prices in $AU (and part numbers for jaycar)



To this you will have to add the cost of whatever you choose to protect your circuit with, for mine I have chosen to pot it to ensure a completely watertight seal, cost of around $3 for the box and around $35 for the potting compound - but I had way to much of that!

Power Consumption

The circuit in its standby condition only draws around 45mA, so is a hell of a lot more efficent than the headlights, once triggered it draws around 300mA, but that will change dramaticly depending on what relay you choose to use.

Basic Functional Description:

The schematic of the circuit you will be building:



The description:

Reference Voltage

R2 and the zener set up a reference point well below the minimum voltage the bike will operate under any normal circumstance (6.8V). The value of R2 is set to limit the current through the zener to just above its minimum current to allow it to operate at the correct voltage. In this case around 38mA

Voltage Sensing

R1 is a 20k potentiometer set to give an output at the wiper of around 6.3V with the bike off and around 7.3 with the bike running.

Comparator

IC1 is set up as a comparator with no feedback (open loop) to allow the output to swing between rails. The output will swing from around 10V to around 2V when the voltage at the -ve input goes above the reference (ie once the bike starts)

Inverter

IC2 is a 555 timer set up as an inverter. When you start the bike and cause the output of IC1 to swing to 2V this will cause the output of IC2 to go from 0V up to 12V applying power to K1 via D2.
The reason for doing this instead of simply swapping the inputs to IC1 is that the 555 can sink and source up to 200mA at its output compared to 20mA for the comparator (IC1), and due to the output of the comparator only swinging between roughly 2V and 10V I found it a lot simpler than setting up a transistor to allow full rail voltage swing (0V - 12V)

The Output

Once 12V is applied to K1 via D2 its contacts will make causing 12V to be applied via D3 latching the relay on regardless of what the voltage on the output of IC2 is. D2 is required to prevent the current being supplied via D3 from flowing into the output of IC2 when K1 is latched and IC2's output goes low. D3 is required to prevent the current being supplied via D2 from trying to drive the load (your lights) thereby exceeding the rated output current of IC2 and possibly pulling its voltage below what is required to activate K1.

Resetting the Controller

Finally the controller will reset when power is removed ie:
When you turn the key off, or;
When you stop the bike with the kill switch and then hit the starter (with the kill switch still in the stop position).

Building the Controller

To build it you will need everything on the parts list, some things may be substituted, or different values used, and feel free to ask if your not sure about something.
First step is to print off the schematic diagram, after that you just follow it and hook everything up as it says. You will need to cut the tracks on the bottom of the vero board to ensure everything is hooked up right, and there is plenty of info out there on the net about soldering and the like so I wont go into that here.

Some pictures of the finished circuit:
The last ones are of the enclosure I used and the potting compound.


















To Be continued in the next post...

Nico
 
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#2 ·
Part 2

Set up Procedure

To save confusion:
When I say turn the bike on, I mean only the key. (kill switch doesn't matter)
When I say start the bike that’s when you fire her up!

When turning the pot slowly you may hear the relay chattering, this is nothing to be concerned about, just move the pot a little further and it will sort itself out, the relay should not chatter during normal operation (once you have it set up properly)

Step 1:
Hook it up as per the schematic ensuring that your relay is rated for the headlight, if you look at the photos of the one I built you will see the yellow box, that small relay runs the big one bolted to the back

Step 2:
Testing the board, With the bike off turn the pot fully clockwise. Turn the bike on, if the headlight comes on, then turn the pot fully counter clockwise and turn the bike off and back on again.
Now your pot will be on the stop one way or the other, with the bike on slowly turn the pot until the headlight comes on. If this works then you have a working circuit ready for tuning so proceed to step 3, otherwise check out you circuit to see where you may have gone wrong i.e. bridged solder connections, incorrect component orientation (pay particular attention to the diodes and ICs), over heated something when you soldered it together (blown up components and or dry joints), or maybe just wired it up wrong. In the case of the last I find it helpful to print the schematic off and red pen each connection as I make it.

Step 3:
Next place a multimeter on pin 2 of the 741 op-amp, note this voltage, and slowly turn the pot so that the meter reads 0.25V to 0.5V below the original reading. If you don’t have a multimeter then you can turn the pot back a very small amount in the opposite direction to what you did to cause the lights to come on in step 2.

Step 4:
Turn the bike off to reset the circuit and test it out!
- Turn the bike on, no headlights
- Start the bike and the headlights turn on

Installing the Controller on the Bike

For starters you will need to know where to wire it in so for that I have drawn it onto the bikes schematic.
Just cut at the red lines and wire it up as shown, please note that this is for an 04RR






I have installed mine under the left hand side fairing with a waterproof connector, I had to move the relays to get it in there but here is what it looks like on the bike:







Enjoy your lights - this could be used for any load on the bike btw (or in a car for that matter)

Nico
 
#4 ·
Why not just:
1) Put key in bike
2) Hold down starter button
3) Turn on ignition with starter held in

Same end result, only this "mod" is free, and doesn't require you to waste hours of your life with fussing with the electronics.
 
#5 ·
Just because I can... electronics is my job and my hobby so I consider the time well spent

I will also have my angel eyes on only when the bike is off, in Sydney your not allowed to have a blue light on the front of a bike (or car) when its running, thats what the yellow line on the wiring diagram is.

Nico
 
#7 ·
So for those of you who may be thinking of building this, you can appreciate the fact that once you pot it in you can no longer adjust it - could be a problem.

So in order to overcome this you will need a 1W resistor and a relay. Depending on which direction you wish to adjust in will depend on where you put the resistor ect.
If your headlights are coming on before you have started the bike then you need to wire it up as shown in the schematic below, if they wont come one at all then you need to wire the resistor (and relay contacts) into the GND line instead.

The schematic:




Nico
 
#9 ·
I wish I was as smart as you............... If you come up with more please post. I will not mock anyone for going the extra yard especially if they enjoy doing it.
 
#11 ·
Anyone know where we can get all these parts in the US? I'd like to try this. I've tried Digikey and Jameco and it doesn't seem like they have everything. I'd also like to get things from one place instead of having to order from multiple places.
 
#13 ·
Have just done a quick search and Digikey has everything you need, just search for the part number that is under the description heading - not the jaycar part number, the only one you may have trouble with is the relay but if you search for "255-2815-ND" you should find it no worries.

Let me know how you go! And if you have any questions just ask.

Nico
 
#12 ·
Nico,

I too am trained in the Electronic Field only since the stupid military has gone to COTS (Commercial Off the Shelf) for troubleshooting and repair, I have since not been able to play or learn any fun stuff with electronics. So as I gain experience in my job I am losing the knowledge I was originally taught.

I don't pay attention to how smart Jessica is, I just want to bang the crap out of her over and over again and then take a hell of a lot of nude pics of her on my bike. Then do it again. Like I care if she thinks buffalos have wings.
I appreciate the fact that some people obviously enjoy their work and hobby enough to share it. Good Day, Mate.
 
#16 ·
Do a search for "490-2976-ND", it will do you just fine.
 
#21 ·
Pretty interesting idea. Great work! :shakehand

Just out of curiosity, if you have a weak battery that doesn't get charged to 14V or the threshold voltage to turn on the lights, that means your light will stay off until you change your battery or adjust the (I assume) potentiometer?

I currently have the timer delay relay and it works about 95% of the time. Sometimes it glitches and turns on my light when I turn my keys to the "ON" position.
 
#22 ·
Pretty interesting idea. Great work! :shakehand

Just out of curiosity, if you have a weak battery that doesn't get charged to 14V or the threshold voltage to turn on the lights, that means your light will stay off until you change your battery or adjust the (I assume) potentiometer?
Yep, spot on. If you are worried about this then you can wire a 12V switching line via a momentary switch onto the coil of the relay - with another diode - so that you energise the relay then it holds itself on.

Nico
 
#24 ·
Yeah, I'm a chemist so this electronic stuff is miles above my head... so, for all us dumbasses, are you going to make these for us? I wouldn't mind giving it a go.
 
#25 ·
I might see about putting together a kit if Moe is happy...

How does something with a prefab board, (instead of the prototyping board I used) all components (minus plugs, potting box and potting compound), and instructions so you know where everything goes?

Just tell me what you think its worth, you can see what most of the components cost in the first post, transfer film for the boards is about $35, a pcb to etch it into is about $20 and the etchant is about $15. Those last three things should be good for about 50 boards though.

I'm also not an engineer so no warranties on the design, and no warranties on your workmanship and as such no warranties on components you have touched. Having said that, the components are all reasonably robust and mine has been in and working a treat for about three months now.

Just remember I'm not a vendor and I don't want to go breaking any rules so this may go no further...
 
#26 ·
Nico - this is pretty cool - these are all really common components (like the 555) which makes it easy to source for the average joe - nice job! I'd use a resistor divider in place of the zener, which would cut your current draw way down.

Good to see there's another electrical person floating around these parts...
 
#27 ·
Nico - this is pretty cool - these are all really common components (like the 555) which makes it easy to source for the average joe - nice job!
Thanks mate, the idea was to keep the cost down as much as possible.

I'd use a resistor divider in place of the zener, which would cut your current draw way down.
If you do that then it wont work. You need the zener to give a stable reference voltage that wont change as the bikes voltage changes, There is a resistive divider on the other input pin of the 741, this is the one that you want to change as the bikes voltage changes. As the voltage changes it will go above and below the voltage set by the zener and the 741 will drive its output to be within about 1V of the rail voltage (because it is in open loop mode). 555 is there to buffer the signal and supply enough current to drive the relay.
 
#30 ·
great job!
Thanks mate!

I had trouble looking for the potentiometer. I wasn't sure which one to use. Everything else I found ok. Thanks for the help. I don't know when I'm going to try this but I know I will.
Did you ever end up giving it a go mate?
 
#32 ·
Well, just to give you an update... the board in the pics above is still running strong in my bike after just over a year so I must have done something right :)

I have done a little more work on this project as well... I wanted another one for my car so I did the board up in a cad program and had it professionally made... this is how they (board house has a minimum order of 10) turned out:

Front and back of the board:


It measures 50mm by 35mm (a little under 2" by 1.4")

So has anyone tried / contemplated making it?
 
#33 ·
Here is the board with the components mounted, now I just have to test it and make sure that the boards are correct :)



 
#34 ·
That's pretty cool. Hopefully, it's easier enough for people to give it a go. Like I mentioned before in my previous thread, the Power-On Delay sometimes have glitches. I'm building a prototype for a friend as a test. Eventually, I wanted to create a simpler circuit that only requires 2 components.
 
#36 ·
Cool, do you plan on posting it up later?

excellent write up Nico, now it makes sense why i always got really good electro advice from you! haha.

good job sir
Thanks mate
 
#38 ·
yep... you can also achieve it with an LC circuit - where the relay coil provides your L...

I wouldn't do it that way, but its food for thought...
 
#43 ·
This may be my own ignorance talking, but what is the purpose of keeping the lights off until the bike is running? My lights only come on with the key turned on, soooooo. I'm just a little confused as to why it matters.
BTW, great and intelligent write up Nico.
 
#49 ·
JMO:

Would you prefer a 555? Cause that's just and RC with a couple of op amps and a resistive divider hooked up to it...

Every timing application out there will be based on an RC or LC circuit until you start looking at decent frequencies, they are cheap, stable at low frequencies and as reliable as anything else suited to the application.

I have used RC circuits much like that with a transistor to hold reset lines low on just about every digital project I have ever designed over the years and have yet to have one fail. Less components generally = long MTBF...
 
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