Voltmeter can measure voltage up to 50VDC. It automatically calibrates when voltage of power supply is unstable.
Project tutorial by IoT_hobbyist
Without hard code, a number of email addresses are set via web. Saved to EEPROM. Arduino sends the notification to these email on events.
Using Serial. println(temp) to send real-time temperature to web. Optionally, we can see daily or hourly graph of temperature in real-time.
Remotely control door via web with pattern password protected. Your door is securely controlled from anywhere through Internet.
Project tutorial by phpoc_man
If door is opened, Arduino sends a message to your Facebook Messenger.
Thank you for your valuable advices,
For the advice to to measure the Vref with a good digital voltmeter, this is a good advice. However, in practical, I think if we have a good digital voltmeter, we don't need to make a DIY voltmeter any more. When I made this project, I just think to the case that someone does not have any voltmeter in hand.
Thank you again for your advice
Hello Don Breedlove,
I did not know your comment soon because I do not receive any notification.
Did you use PHPoC Shield, or any other shield?
Or connect with your social account:
New here? Create an account