Finished Motorcycle Module Project

[Rexlan]

Thanks to MikeMI for the help on the high side switching.
This is a finished project and may save others considerable time. It works perfectly too! I had to use this special PFET because of the physical size. A TO-220 would have been better but it just would not fit in the 3 x 1.5 enclosure.

This is for my motorcycle and has a lot of function.
I ended up with 30 (extra) circuit boards because I had a ground plane issue on the first run. I repaired them by scratching it off around the laid down PFET and it does not show ... but it isn't right either!

If anyone wants a programmed processor and a circuit board I will furnish it for $25. Send me an email. You can source the remainder of the parts from Digi Key with the parts list for less than $25. The hard-to-get one is the PFET from Fairchild and the only source I can find today is Electronic Component Distributor | Onlinecomponents.com and they will probably get scooped up soon. There is a 13 month lead time now!

All three of these function cost about $325 and that is why I built my own. I've attached the schematic for anyone to use. I did it as a hobby and not to make a buck.

Features:

1. Headlight modulation on/off at 4 Hz - automatic disable at dark.
2. Brake light modulation with 4 quick flash then steady on like normal.
3. Automatic turn signal cancellation after 10 seconds. Remains active if brake is activated within the 10 second time and while the brake is on steady at an intersection.
4. If the turn signal is canceled automatically bu the unit and you forget to reset the turn signal switch, the unit will beep the horn in 20 seconds. It will do this 4 times then quit. This is not blowing the horn - very short beep just so you can hear it.
5. The turn signals and the brake light are driven directly so you can use any size/type bulbs, including LED, withing the current limits.

Thanks to the forum for the help.

 

[magnatro]

PIC axe based... hmmm.

 

[picbits]

Brave man using a 7805 without any additional protection in an automotive application. You might want to consider adapting it slightly to use a LM2940 or similar with a low ESR output cap (check the datasheet).

I've seen some spectacular failures on automotive stuff with the 7805 - I use them on my own products but with a fair bit of input protection and filtering - at a minimum I have a couple of resistors, a diode, caps, a transzorb, fuse and zener before the 7805. On some of the newer stuff I'm designing I'm using a P channel Fet as a preregulator to protect against load dumps etc.

 

[MrDEB]

Definality use a LDO regulator such as the LM2940 or the LM2950
That circuit is bound for failure without a LDO regulator.

 

[MikeMl]

An LDO is NOT required; the OP has a minimum of 7V of headroom to operate the 78L05 regulator. What is being suggested is that there are linear regulators available specifically designed for automotive applications that include some measure of protection for load dumps, and transients.

Putting a series 150Ω resistor between the +12V and the 78L05 input pin would go a long way to improve things. Adding a 15V Zener, cathode to 78L05 input pin, anode to ground, would make it sufficiently bulletproof...

 

[MrDEB]

The LM2940 is DESIGNED for automotive use. I would trust an LDO before using a zener.
The LM2940 or the LM2950 (need to recheck data sheet) can run with very little headroom.
The problem is the automotive electrical system is very noisy and full of spikes. A 7805 will not last very long. Its not designed for automotive use as is the LM2940/50 LDO regulators.
READ the data sheet

 

[MikeMl]

...I would trust an LDO before using a zener.

Do you even know what LDO means? It means Low Drop Out Regulator. There are hundreds of LDO voltage regulators available which are not specifically designed for automotive applications. Just because a regulator is "LDO" says nothing about its applicability to the automotive environment.

The LM2940 or the LM2950 (need to recheck data sheet) can run with very little headroom.

As I stated earlier, this application does not need a Low Drop Out Regulator because there is more than 7V of headroom available. You might be looking for a LDO if you wanted to make 5V out of 6V input.

The problem is the automotive electrical system is very noisy and full of spikes.
A 7805 will not last very long...

That is your opinion. Have you ever taken a data aquisition system for a ride in your car or in your airplane to record the bus voltage? I have done both.

Spikes due to inductive loads being switched on/off are not the problem. They are easily controlled by a simple series R and shunt C at the input of the VR. The battery impedance is so low that it acts as a several Farad capacitor, and it does a very good job of leveling anything that happens while it is in place.

The difficulty stems if the battery is accidentally or intentionally disconnected while the engine is running. This precipitates an event called a "load-dump", where the system voltage can swing up to ~60V for a duration of tens to hundreds of ms and that is where the series resistor and shunt Zener comes from.

 

[picbits]

As above - the 7805 can be used in automotive applications but make sure you protect it against the spikes etc.

I've sold maybe 80 units of a particular product. I make the whole thing inhouse including the PCB etching. Around 50% of the cost of the unit is made up of protection devices.

Over the past 3 years of selling them I haven't had a single failure.

Someone else on here made something for a friend with a 7805 regulator and no protection - it lasted minutes and took out his microcontroller when it went. After a few of these failures I think he cottoned on that it wasn't good to use a bare 7805 with no additional protection.

 

[Rexlan]

As above - the 7805 can be used in automotive applications but make sure you protect it against the spikes etc.

I've sold maybe 80 units of a particular product. I make the whole thing inhouse including the PCB etching. Around 50% of the cost of the unit is made up of protection devices.

Over the past 3 years of selling them I haven't had a single failure.

Someone else on here made something for a friend with a 7805 regulator and no protection - it lasted minutes and took out his microcontroller when it went. After a few of these failures I think he cottoned on that it wasn't good to use a bare 7805 with no additional protection.

Hey ... me either. Not a single failure in 10 years with the 78L05. Overkill is not my cup of tea - perhaps you should try my design?
I may add a series R in the fuse per Mikes's suggestion though ... makes sense.

I build this also and did the Hardware/software and it too works perfectly with that 78L05. I have over 100 of them out and they just keep on timing!
**broken link removed**

 

[amitpj]

how power did u used ..

 

[picbits]

Hey ... me either. Not a single failure in 10 years with the 78L05. Overkill is not my cup of tea - perhaps you should try my design?
I may add a series R in the fuse per Mikes's suggestion though ... makes sense.

My theory is that for every unit I get back, the loss I make in time, postage, hassle from customer plus getting another unit built and sent out offsets the cost of the protection components in 20-30 units. The market I have is full of people who retrofit engines/dashboards etc into their cars so the chance of load dump / incorrect wiring is much higher so I always err on the safe side when it comes to designing stuff lol.

Some of the newer stuff is designed around the LM2940 but I still make sure there is additional protection on the modules "just in case".

 

[DirtyLude]

Those headlight modulators are so annoying.

 

[BrownOut]

Those headlight modulators are so annoying.

They're supposed to be, Heh!

 

[DirtyLude]

I'm not convinced of there effectiveness and being forced to stare at them on a long straightaway or in my back mirror on the highway makes me want to punch people. Best I've seen is the separate light units that people actually turn on/off when they are in area's of traffic with intersections or even the ones with smooth pulsing rather than flickering.

 

[BrownOut]

Who forces you to stare at them?

 

[DirtyLude]

Who forces you to start at them?

Are you serious? You can't avoid seeing the vehicle that's heading towards you in the opposite lane.

 

[BrownOut]

I don't try to avoid it, but I don't have to stare at it either.

 

[DirtyLude]

I don't try to avoid it, but I don't have to stare at it.

I don't understand. Are you just trying to argue? Why are you taking this 'staring' reference so literally? It's in front of you, facing you, and it's annoying and distracting to drivers.

 

[BrownOut]

Well, driving requires some discipline. If you find yourself being distracted, you might want to work on that. The flashing lights are a safety feature for low visibility vehicles like motorcycles. It's not perfect, but it's a good thing.

 

[DirtyLude]

Well, driving requires some disclipline. If you find yourself being distracted, you might want to work on that. The flashing lights is a safety feature for low visibility vehicles like motorcycles. It's not prefect, but it's a good thing.

I won't argue it here, but the 'safety' of these devices have been argued to death on motorcycle forums. I've been riding for 30 years and though I see it being helpful specifically with the blind left turners I think the distracting qualities are more of a problem then a benefit on the road.