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Topic: Love-o-meter : Big Love.... (Read 517 times) previous topic - next topic



I have implemented the project number 3 : the love-o-meter.

Once the first LED is lit, measured temperature is getting very high (more or less +10 °C for each LED which is lit).

As required in the book, each of the 3 resistors is 220 Ohm.

By switching to a 10 kOhm resistor, project works properly.

By measuring tension (Volt) around the TMP device, when temperature is getting very high, it goes from 5,07 V to 4,77 V : more or less 3 * 10 °C, because of 3 LEDs ? Maybe just coincidence.

Does anyone have an explanation ? Has someone faced the same situation ?



Hi, I'm facing the exact same situation. I think even the small load of 2 LEDs decreases the Arduino board's 5V pin voltage, affecting the TMP36's output.

I measured more or less the same voltage drops on the TMP36 as you did.

The approaches I'm planning are:
- switching to an external power supply (no PS from the USB port, but using the jack)
- using bigger resistors


Aug 19, 2018, 09:59 am Last Edit: Aug 19, 2018, 10:26 am by fostgate
Hi Guys,

I got exactly the same behavior. Each LED which is turned on increases the voltage on the measured analog input. Normally in bigger ECUs the ground for digital and analog input signal are separated because of the "dirty" ground a digital signal often brings with itself. But its hard to believe that only one LED has such an influence and that this has not been tested by the Arduino team. Because the result is that always all three LED are set to HIGH. If this would be a general problem more people should react on it. Maybe it is a hardware issue of some boards? What do you think? I don't have a solution here, but an answer or statement from the Arduino guys would be nice.


After I played around a little bit with the ground connection (e.g. moving the cable or moving the connector a little bit in the pin hole of the bread board) I found out that the ground connection was (or still is) not very good. I realized a big influence of this cable movements to the measured values in terminal (up to 300mV). After I plugged the ground line in and out the breadboard a few times the measurement became better and more stable. But it is still sensitive if I move the cable (even if much better now). So after all I think if the ground is connected properly, the measurement became more stable. The voltage toggles about 20mV now.

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