# Voltage regulation to 5v in a 6v classic car environment

Hello all,

I have a 1950 split window beetle and want to implement an Arduino Nano.
Its electric environment comes with a 6v generator incl. a mechanical 6v regulator which results in a voltage of 6.2 up to 7.2 depending on the load and the rpm. And shure I guess there are lot of noise and maybe spikes in the signal, so this I have to take into account when feeding the Arduino with the car's voltage.

As the drop from 6-7v to the Arduinos 5v is quite low I thought about two approaches:

1. A small voltage DC booster device which comes with all needed Arduino voltage safe components on board. The booster would increase the voltage from the cars 6-7v to i.E. 10v which can be directly provided to the Arduinos VIN.

1. A classic voltage clamp approach using a zener diode and a resistor in front.
Now ... as here also the voltage spikes and noise of the vehicle have to be taken into account ... can this approach be optimized by using capacitors behind and in front of the zener diode?

See the idea below.

If this 2nd approach would be a good choice to go with, can this also be 1:1 used in a 12v car electric environment?

Andrew

Personally, I would use a BEC for this. Seems ideally suited.

A GOOD one: MAXAMPS high current version

Maybe a lower current one is needed though... this is just the general idea.

Your second suggestion is no use at all, it can supply only very limited current, as determined by the 100 ohm resistor. If the battery voltage is 6V and the Zener diode is 5V, that's 1V across the resistor. 1V/100 Ohms means a maximum of 10mA. Not much use for anything.

I suggest a buck / boost converter with a 5V output. A buck / boos converter can take an input below, at or above the desired output and still give the output you want. Plenty for sale on your favourite sales web site or electronics component supplier.

I'd probably just take a chance and connect Vin to the 6V power. In general, linear regulators are reasonably-good at taking-out spikes and the Arduino should continue to run if the regulator slightly drops-out of regulation and you end-up with less than 5V.

Worst case you fry the Nano. Next-worse, you get glitches that cause unreliable operation.

...I've got an Uno in a 12V car powered from Vin. No problems..

PerryBebbington:
Your second suggestion is no use at all, it can supply only very limited current, as determined by the 100 ohm resistor. If the battery voltage is 6V and the Zener diode is 5V, that's 1V across the resistor. 1V/100 Ohms means a maximum of 10mA. Not much use for anything.

Thanks for the info, I see your point. But just for my understanding, .... what would happen if I just remove the resistor as the Arduino would not consume that much current so the Zener won't fr, correct?

AndrewCologne:
Thanks for the info, I see your point. But just for my understanding, .... what would happen if I just remove the resistor as the Arduino would not consume that much current so the Zener won't fr, correct?

The Zener diode most certainly WILL fry! If you have a 5V (without checking I think the nearest voltage to 5V is 5V1) Zener then it conducts for any voltage you apply over 5V, and it conducts rather a lot. What you are suggesting is that there would be 6V at the battery end of the wire but only 5V at the Zener diode end. Bound to end up with smoke.

Have a read of Zener diode

DVDdoug:
I'd probably just take a chance and connect Vin to the 6V power. In general, linear regulators are reasonably-good at taking-out spikes and the Arduino should continue to run if the regulator slightly drops-out of regulation and you end-up with less than 5V.

Worst case you fry the Nano. Next-worse, you get glitches that cause unreliable operation.

...I've got an Uno in a 12V car powered from Vin. No problems..

AFAIK many people here recommended not to connect an Arduino to the vehicles electrical environment directly.a
Beside this ... I thought the Arduinos VIN accepts voltages till 12v? And the cars voltage is about 13-14,4v when engine is running.

DVDdoug:
I'd probably just take a chance and connect Vin to the 6V power. In general, linear regulators are reasonably-good at taking-out spikes and the Arduino should continue to run if the regulator slightly drops-out of regulation and you end-up with less than 5V.

You need a properly low drop-out regulator for this, the on-board regulator probably needs 2V headroom.

Given the quality of automotive supply voltage using a boost-regulator to 10V into Vin is a reasonable plan too,
which may handle the odd drop out in battery voltage better (if the boost regulator has a low enough minimum
input voltage).

AndrewCologne:
AFAIK many people here recommended not to connect an Arduino to the vehicles electrical environment directly.a
Beside this ... I thought the Arduinos VIN accepts voltages till 12v? And the cars voltage is about 13-14,4v when engine is running.

You haven't read the OP, this is a 6V car.

Is running a 3,3V Arduino from Vin an option?
That would be the easiest way to get a reliable operation from 4.5-8V without additional hardware.

MarkT:
You haven't read the OP, this is a 6V car.

I was the one with the 6v car, the author I refered to gots a 12v car and I was wondering as his Arduino actualy will be fed by 13-14v.

RIN67630:
Is running a 3,3V Arduino from Vin an option?
That would be the easiest way to get a reliable operation from 4.5-8V without additional hardware.

Yes, that could be an option too.

Thank you all for your input

Are you going to disconnect the Arduino while you are cranking the starter? The voltage then drops to 3-4 volts.

Paul

The OP circuit #2 will slowly drain the car battery. Circuit #1 also, but not as badly.

Paul_KD7HB:
Are you going to disconnect the Arduino while you are cranking the starter? The voltage then drops to 3-4 volts.

Paul

Does the car have a starter?

Yes .. its from 1950 but already comes with a starter

++Karma; // Beautifully restored and maintained

AndrewCologne:
Yes .. its from 1950 but already comes with a starter

Beautiful!
And what is the arduino supposed to do?

It might have been mentioned before however; is this vehicle positive ground? It it is it won't matter that much but filtering the input will be slightly more difficult.

That ever method you chose, you should add:

a hefty 12V transorb
0.01µF capacitor
100µF capacitor

all in parallel with each other and close to the input of your powersupply for the board.

If positive gnd, you will also have to consider how your inputs are effected.

@ Perry and Ring
Thanks for the flowers!

This car is negative ground with standard Bosch electring wiring concept and terminals

The Arduino is a project for ... 1. a digital regulator for the cars generator/alternator
and 2. a special flashing relay devidce where also the semaphores indicators at the sides will be protected from burning as after 1 minute they should automtaically switch of etc etc etc.