I am also controlling temperature using a LM35 (GND, VCC and Signal). Temperature is pretty stable, the problem is:
When my temperature is OK, my relays are OFF and arduino 5V supply is around 4.8V (no problem)
When my temp is below my reference, I want to switch on relay. While switched on, my arduino supply decreases around to 3.8V, and them my LM35 "jumps" around 5 degrees.
How can I, electronically, remove this decrease step of supply?
Should I try some capacitors or resistor in series?
I would really be very glad with some help, Thanks in advance.
The coils takes too much current. Feed them from other source than the arduino
(4x AA , cellphone charger, a diffrent USB-port. anything but the Arduinos onboard 5V)
knut_ny:
The coils takes too much current. Feed them from other source than the arduino...
That's certainly the obvious answer and the best if it's practical but there are two other potential ways around the problem given that the TM35 draws very little current.
The first would be to operate the TM35 at a lower supply voltage, supplying Vs from a LDO (low dropout voltage) voltage regulator connected to the Arduino 5V supply. As the minimum supply voltage for the TM35 is spec'ed at 4.0V, and there would be a small voltage drop across the LDO, that's not practical unless you can get the loaded Arduino supply voltage a little higher.
The other potential solution, if you're prepared to add some components, would be to supply the TM35 from a voltage doubler or multiplier circuit supplied by the loaded Arduino 5 supply. A LDO would probably be advisable between the voltage doubler output and the TM35 Vs. Google 'voltage doubler' or 'voltage multiplier' or search the forum for details.
Another possibility would be to use a small dc-dc converter module. For any of these options it would be as well to ensure that the output voltage supplied to the TM35 is reasonably clean with minimal ripple, so that stable temperature values are obtained..
