Car power supplying Arduino??

Using Arduino Project Guidance
1

Thanks for viewing my post.

This is the project: I need to power the Arduino Uno from the car battery 24/7 in the winter to activate a remote starter at a predetermined time each day.

My first concern is the current trickling to the voltage regulator will draw too much from the battery?
-The voltage regulator is a DC/DC Converter Breakout board (BOB-09370) from www.SparkFun.com
Which utilizes a Lineage Power 12V Pico TLynxTM 6A: Non-Isolated DC-DC Power Module

The car has a average voltage of 14.4vdc, and will not start below 13vdc.

IS THIS A GOOD CHOICE FOR A POWER SUPPLY?

2

Yes. Use a switching type DC to DC converter, It doesn't need to be isolating.

Because the regulator in the Arduino is "linear" which means it takes current to do the regulation (well a lot more current than the switching type)

Also as its linear it needs to dissipate the energy (Volts x Amps) of the voltage its regulating over i,e 14 - 5 V = 9V.
so if the Arduino is taking perhaps 0.1A, that would mean that the regulator would take at least 0.9W all the time (much more than the Arduino its self)

One question. why do you need to power the Arduino all the time (they don't make good clocks), just connect it to the circuit in your car which is powered when the key is turned (often termed as when the ignition is On )

PS. Plenty of places sell those DC to DC regulator converters. I bought 10 of them from eBay a while back for about $2 each

3

That is good to know, thanks for the reply.

So by using this regulator it will result in a lower current draw. I only wanted it powered all the time so the Arduino can monitor the time from a Chronodot RTC. I have a description linked here: 'Car Remote starter timer integration - Project Guidance - Arduino Forum'

It would be nice to have the Arduino go into its lowest power mode while waiting to trigger the next daily car starting. Powering it while standing by is what may draw too much current. I could install a 2 Watt solar car battery charger that would offset standby current draw during the day.

Do you think the milliamp draw is negligable from a car battery?

4

I need to power the Arduino Uno from the car battery 24/7 in the winter to activate a remote starter at a predetermined time each day

If you are start the car every day, the discharge from the starter is about a million times more than the Arduino would take all day.

Just run the car for a few more seconds each day and you'd have plenty of power to run the Arduino.

5

Thanks RC, I will carry on with the project to power the Arduino.

The next step is tuning the trim pin on the voltage regulator to get a 5v output. I am thinking of putting the DC/DC Converter Breakout board (BOB-09370) from www.SparkFun.com onto another blank breakout board and use a trim pot to get to 1350 Ohms. There isn't enough space on the little board to get the required trim resistors installed; with the larger board underneath there will be room for some nice screw terminals for input/output conductors.

All of this will be mounted inside a 6 x 6 x 4 inch PVC Hammond enclosure.

6

The car has a average voltage of 14.4vdc, and will not start below 13vdc.

IS THIS A GOOD CHOICE FOR A POWER SUPPLY?

:roll_eyes:

Average voltage is 14.4v is it?
Car refuses to start under 13v

And who took these measurements? Average voltage from the alternator is around 14v the car would have issues if the battery read 11.5v (starting it) but 12.5v to 13v is plenty to turn the starter motor...

your values seem off.

7

It could be my cheap Green Lee meter.

Haven't sprung for the Fluke.

8

I agree with @cjdelphi those numbers are a bit high.

When the engine is running you could get 14V or more, but most cars will start at way below 13V ie the battery supposed to give 12V and under load of the starter will drop down even lower.

9

Sometimes when I try and start the car the heater goes on and the power antenna goes up, the car will not start.

I think the accessory motors are drawing too much current, so much that the intended starter is drawing locked rotor current and is starved, and cannot rotate.

Any thoughts?

10

Which heater are you referring to, the fan motor that blows the air. That won't take a lot of current, and antenna motors don't take that much either.

The symptoms are of either and old and tired battery, or bad connections to the battery, either at the battery (very common) or at the GND where the -Ve of the battery is attached to the chassis metal of the car

11

Sounds to me you have other serious problems in the electrics somewhere.

....maybe like feedback from adding extra circuitry perhaps..???

On the original subject, run the arduino off a standard 4cell nimh pack and recharge that via a small regulator such as the usb charger type each time the engine runs.

Probably not such a good idea having engines starting without warning by automatic means unless limited access provisions are in place for safety reasons.

12

it sounds like something's drawing too much current already that or the battery simply can't provide the cca required to crank over the engine, the start motor could be also on it's way out? whatever the cause...

I think trickle charging a small battery so it's under it's own power when the alternator is off this gives a UPS effect.

13

bluejets:
Sounds to me you have other serious problems in the electrics somewhere.

....maybe like feedback from adding extra circuitry perhaps..???

On the original subject, run the arduino off a standard 4cell nimh pack and recharge that via a small regulator such as the usb charger type each time the engine runs.

Probably not such a good idea having engines starting without warning by automatic means unless limited access provisions are in place for safety reasons.

I have added a few things, a remote starter module, USB port power with key on, and a one-shot 2 min delay on relay to keep the heater blower fan off while the car starts and warms up. Also, I have disconnected power to the antenna in the winter so it doesn't freeze.

I agree that there are safety concerns, the neutral safety switch is bypassed for remote starting; I couldn't track down the right wire. The vehicle is always locked so I am not too worried about tampering. Do you think a short horn blast would be sufficient to bring attention to the vehicle seconds before starting?

To use the battery pack you suggested, it would maybe only need 12 to 24 hour capacity. Do you think it could handle that at -30C?
Great idea though, it would be nice to completely isolate the arduino power source. In the winter if the car battery dies it can be a hassle, being late for work or class.

Thanks for the suggestion.

rogerClark:
Which heater are you referring to, the fan motor that blows the air. That won't take a lot of current, and antenna motors don't take that much either.

The symptoms are of either and old and tired battery, or bad connections to the battery, either at the battery (very common) or at the GND where the -Ve of the battery is attached to the chassis metal of the car

Thanks, I checked the chassis to battery ground and it is very rusty and corroded. Will replace soon and sand off the rust.