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enter image description hereI am trying to simulate a heating system using an atmega32 microcontroller, 4 lm35 sensors, and Proteus software for circuit simulation. Unfortunately, whenever I run the simulation I encounter the error:"'Power Supply' (330mV) is outside the specified range (3.5V-30V)" which says that the sensors are not getting enough voltage to start working. This error pops up when I connect more than 1 lm35 sensor to the ADC pins of atmega32(port A). When there is only one sensor it works correctly. Can anyone help me with this problem?

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  • \$\begingroup\$ Are you sure the MCU pins are properly configured as analog inputs? \$\endgroup\$ Dec 26, 2017 at 4:51
  • \$\begingroup\$ yes, PORTA is the only port in Atmega32 which can convert analog signals to digital. \$\endgroup\$ Dec 26, 2017 at 8:09

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Most of digital ICs (MCUs, logic gates etc) in the ISIS library have hidden VCC/VDD pins. By default, they are not shown in the schematic but are designed to connect automatically to POWER terminal (the terminal with the up-arrow symbol). Yeah, it's 5VDC but it's not suitable for powering analog ICs like LM35.

Replace them with a "DC" source. You can find it under GENERATORS group to the left (the circle with a blue sine-wave symbol inside it). Place one, double-click on it and set the voltage to 5.

Note that if you're planning to transfer this circuit to ARES for PCB design then it will be problematic because of that POWER terminal.

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  • \$\begingroup\$ I did that but the same error happened again! \$\endgroup\$ Dec 26, 2017 at 8:08
  • \$\begingroup\$ I've Proteus 7 on my Lab PC and I tried a similar thing: If I don't connect LM35's supply pin then I get the same message (not error, just a message with exclamation icon) but the simulation still goes on. If I connect it to a POWER terminal or a DC supply then I get no messages. I think you should make sure that the sensors' power pins are connected to the supply. Don't put an individual POWER terminal or a DC source for each sensor, connect all the sensors' power pins to a single supply instead. \$\endgroup\$ Dec 29, 2017 at 5:31
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Double click on every power supply symbol and add +5v, don't forget +.

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