Electrical – A circuit to fade-in and -out LEDs (DRLs) only when the car engine is running

Has anyone done any work in this field?

Wireless data acquisition is quite common in many different industries. I am doing some work in industrial computing and am actually using both bluetooth and cellular data networks simultaneously in an embedded solution. Just google something along the lines of "Sensor Data Acquisition" and you can find a plethora of articles.

Can you give me any information on what works and what does not?

I could give you information on what worked and didn't work with my specific application - but beyond that I wouldn't be helpful. The problem is this question is incredibly vague and you would need to specify operational constraints, design specs, goals, etc in order for any of us to give you an idea of what you need to head. Luckily however I can kind of point you in the right direction.

You are doing something that has been done many different times and in many different ways - use that to your advantage. Before you design anything you need to explicitly record what you are trying to accomplish. From there you can start designing. Generally speaking this project is going to be broken up into generic parts:

Device Communication

How exactly does your device need to be communicated with? You need to understand what protocol it uses and the hardware needed to communicate with it. Once you can get data back from your device you have your foot in the door and are ready to go.

Data Transmission Once you have your data are you going to send it in raw form? This could be in binary, hex, octal, etc. Or are you going to put it into a nice parse-able XML format that separates sensors and registers into a logical grouping.

Data Viewing How are going to view this data? Are you going to just use a Bluetooth serial link and read off of it like a virtual serial port? Is there going to be an intermediary database? Etc.

Will the electrical fields from the motorcycle engine interfere with the Bluetooth data?

There is a good chance that the loud signals from the ignition,alternator and other noise generators could affect your device. But like we said above, this has been done before so there is tons of information out there on EMI shielding, EMI measurement techniques etc. Also, many different types of modular EMI enclosures exist to house your project.

In Conclusion

Figure out what you want your project to do and how you want it to perform. Don't be afraid to do some research, even if you don't know exactly what you are looking for. Here are some good starting points though:

• Bluetooth Data Acquisition
• ODBII Bluetooth Communication

Device load is 1 Ampere at 11 Volts. Capacitor bank should sustain this power for 4 seconds, before dropping voltage below acceptable (unspecified) threshold voltage. Let's say a drop down to 10 Volts is acceptable.

• 1 Farad = 1 Ampere-Second / Volt

For 1 Volt of drop, over 4 seconds, at 1 Ampere,

• F = 1 x 4 / 1 = 4 Farads

Thus, required capacitors must total 4 Farads, with a recommended voltage rating of ~ 24 Volts or higher: Car electrical systems can see voltage spikes of over twice the nominal voltage in certain situations.

For charging the capacitor at start-up, the battery must support the inrush current the capacitor bank will draw. As car wiring and batteries are typically very low resistance, given that 100 Amperes or more may be drawn for starting the car. A discharged capacitor behaves pretty much like a short circuit initially when connected to a charging source, so 100 or even up to 1000 Amperes could well be drawn by it.

Solution:

Use a bank of car audio capacitors that incorporate soft-charge circuitry into the capacitor units. These are in the $100 to $200 range. Keep in mind, though, that car audio capacitors are typically rated far higher than their actual capacitance:

For instance, this 10 Farad rated capacitor was found to actually be a mere 0.227 Farads.

The typical naïve car mod customer never figures it out, so the manufacturers continue to sell them.

Please note:

Like I have implied in comments, this capacitor bank approach is non-ideal, could be dangerous, and is actually strongly not recommended. I've put down the numbers simply because that's what the question asks for.

Both the answers posted at this time other than mine, actually point out the more practical approaches to the problem:

• Either turn off the lights at crank time, or
• use a different power supply, i.e. a SEPIC or buck-boost.

Both those much more practical solutions have been rejected by the OP.