But why isn't the TS using the 5 V regulated output from the Arduino board?

 

But why isn't the TS using the 5 V regulated output from the Arduino board?

Because:

I believe it's recommended that you power a nano with < 9 volts to prevent overheating the voltage regulator.... even w/o powering an additional 25mA load.

 

Because:

The Vin is rated for the 12 V. If it can't operate properly on a voltage input it is rated for, that doesn't say good things about the design.

But it would be better to drop the 12 V using diodes, if nothing else, and use a regulated 5 V output for the sensors.

 

The Vin is rated for the 12 V. If it can't operate properly on a voltage input it is rated for, that doesn't say good things about the design.

Yep, Vin is rated for 12 volts. But a quick search shows that people have had overheating problems when doing so. I can't vouch for the accuracy of those statements, but there are plenty of them around.

Maybe overheating is a myth, maybe not. But apparently this is for a device that has to be reliable over the long term. Buck converter modules are cheap and don't require much real-estate. Seems like it's a prudent step to me. The alternative is to supply 12v to the Arduino and use its on board voltage regulator. If/when it proves to be unreliable others can be blamed for a poor design.

 

Sounds like a typical not accounting for wattage situation.

Poster says: My transistor keeps burning up, it's rated for 60-volts and 1 amp.

Yea, but not at the same time.

 

Far more stable is an LM78L05, or a LM7805. Cheaper and simpler.

 

Cheaper then what?

 

Far more stable is an LM78L05, or a LM7805. Cheaper and simpler.

Cheaper? Pennies perhaps. Mini 360 dc-dc buck converter modules can supply 3 amps and can be had for 36 cents each or less. They may not be necessary for this application drawing 25mA, but they're not going to hurt anything either.

 

I was referring to products that I would trust. Those ain't them!!

 

I have used a number of them without problems. They are a cloned common design with I'm sure tens of thousands in use.

I've made 3 valid points here:

1. A voltage divider should not be considered as a power source. I showed the WHAT – I suggest it's a good exercise to apply Ohm's Law to understand the WHY.

2. I've indicated that some people have encountered problems when an Arduino is powered by more than 9 volts, and that for maximum reliability, a 5 volt regulator should power both the Arduino and external loads.

3. I suggested the a buck dc-dc could be used to cut heating and power dissipation.

Beyond that, I'm done.