Powering imp via car electrical system

Hardware
1

I see the April dev board can handle a voltage from 3.3 to 17 volts. I’m curious to know if there are any cautions/recommendations about powering it directly via a 12vdc car/boat electrical system in the corresponding vehicle.

On the boat front, I have a friend who has experienced issues with his battery draining due to some unknown load. There is WiFi at the marina. I was considering offering him a quick solution to notify him when the battery drops below a specified voltage. It could also be used to alert of potential freeze conditions if his heater fails during the winter months.

On the car front, I was considering getting engine data whenever the car is in/near the garage via an appropriate OBD adapter. I haven’t really given this one much thought, but I’m still curious to know if there are cautions about power.

2

Should not be a problem to connect it to their batteries. As long as they stay within the range the regulator is capable of handling.

3

Car electrical systems do nasty things. I’d recommend (a) a 100v diode in series with the power input (to catch negative voltages) and (b) a 16v transient suppressor across VIN/GND. You can see load dumps of 100-200v when turning off a car; I know nothing about boat electrical systems though!

Really, you want to have a higher rated PSU to give more headroom for the transient suppressor (eg varistor, tranzorb, etc) to work before the PSU helpfully self-destructs.

Or, easy option: buy a phone charger and run the imp from that. The charger will have all this stuff inside it alrady.

4

Try opening a cheap phone charger. :wink: 7805 inside, maybe a resistor to make the phone charge faster, and overheat the 7805.

I had another supply in my old car to power an arduino, after 5 years it still was running fine. But I never checked how well it worked, regarding noise and such. It just did the task I had it to do.

5

Very helpful feedback! This forum is great! I think I’ll go the phone charger route.

6

You say the marina has WiFi …

To access their WiFi, do you have to pick the ID from the wifi list and enter the password … just like the WiFi in your house?

Or do you have to access a “webpage” they have, using your browser, where you log-in?

The webpage type of access is “captive WiFi”, and you won’t be able to use the imp.

7

Yes, I’ve encountered that issue numerous times at our customer sites. I’m hoping they don’t require acknowledging appropriate Internet behavior via a webpage. The other issue I come across (as recently as this AM), is a “guest” network that only allows port 80 traffic.