Powering Arduino on a 6 volt automobile

I have successfully built a temperature gauge for my 1937 Ford, using a 5 Volt Nano and a 10 LED bar. It works very well. Next I have to power this project from the 6 Volt system of the 1937 Ford. The Battery voltage varies from a little over 5.0 volts to nearly 8.0 volts. I don't think that a 7805 voltage regulator will work, because of the low voltage that can occur on this car. My next idea was to make a dc to dc switching power supply. I've made a few in the past (boost supplies), but the input voltages were always lower than the output. Does anyone have a suggestion as to how to provide a good power source for my project? Thanks, Mike

The V-in (RAW) pin of a (classic) Nano is the input of a built-in 5volt regulator, and is designed to take that supply voltage range. The only worry would be that battery voltage is 'dirty' (high voltage spikes).
Decoupling capacitors, and maybe a 12volt TVS diode could combat that.
Leo..

Classic Nano? Would that be an Italian one? I was using a cheap from Elegoo, Chinese? I'll try, raising the voltage on the Elegoo board and see what happens. Thanks, Mike

The Battery voltage varies from a little over 5.0 volts to nearly 8.0 volts.

This seems strange in a 6 volt system.
Voltages seem outside of the normal range one would expect.
There are low dropout 5 volt regulators.
https://au.rs-online.com/web/p/voltage-regulators/2988491/?cm_mmc=AU-PLA-DS3A--google--PLA_AU_EN_Semiconductors_Whoop--(AU%3AWhoop!)%20Low%20Dropout%20Voltage%20Regulators--PRODUCT_GROUP&gclid=Cj0KCQjw24qHBhCnARIsAPbdtlJ9qni6SMGyvU_Qah_hi7uabCyzwqaxTiuDD1bPjopJtFMQo_x4qO0aAoTsEALw_wcB&gclsrc=aw.ds&matchtype=&pla-300095888546

You have to remember that the old generators only put out maybe 12 amperes or so. They didn't imporve until later. When the headlights are on and if you turned on the radio ( a heavy load) the voltage can drop to under 6.0 volts. I'll try one of the low drop out regulators, The under 6.0 volts conditions are limited. Thanks for the reference. Mike

And a mechanical voltage regulator. Starting the engine may drop the voltage to 4 volts or so, depending on the age of the battery. Some people used 8 volt batteries and cranked the regulator up to keep it charged. Thinking of a 1952 Oldsmobile V-8.
Paul

No, just a basic 5volt Nano V3.0.
Arduino have since released newer boards, which they confusingly also have called Nano.
Nano Every, Nano BLE, etc.

Don't know if your setup can handle lower supply voltages (the Nano itself can to some extend).
Maybe you could switch to a 3.3volt type.
Leo..

1 Like

The cheapest crystal might stop below freezing temperatures ( 0°C ). The official Arduino boards use better quality components.

The Nano will probably still run with 4.5V to the RAW pin.

If you really want 5V, then there are buck-boost converters. They convert anything to 5V.
See: https://www.pololu.com/category/133/step-up-step-down-voltage-regulators.

With or without such a converter, you still need extra protection against high voltage spikes as Wawa already wrote.

Some very good ideas, thanks. I first want to resolve the power supply issue. Once that works then I'll add the needed protection and maybe worry about the ambient temperature variations. Thanks again, Mike