Starting from scratch

I'm a homebrewer and wanted to automate some of the tasks such as keeping my freezer at the perfect temp, Shutting off a gas solenoid to maintain a boil, etc. I thought of getting a Arduino Mega 2560 rev3 with a temp probe and a power tail to control the freezer. My question, is that the route i would go for that or should I seek some other way to do it? I'm new to the microcontroller scene but i'm willing to learn.

Explain problem statement properly.Put some picture of ur setup. What you want to control and what kind of sensor your using.

Sorry for being so vague. The intended use would be to have an ambient temperature from inside of the freezer monitored by a temperature probe such as the dallas then have it report to the contoller which would in turn would trigger a relay or powertail to turn the freezer on or off to maintain a given temperature.

if i rightly understood. you want to trigger relay if temperature exceed particular limit.

Here problem statement is not clear. 1) temperature limit 2) type of sensor being used to measure temperature 3)What is action relay will take means to say where it is connected ?? to what it is connected.??

AMPS-N: if i rightly understood. you want to trigger relay if temperature exceed particular limit.

Here problem statement is not clear. 1) temperature limit 2) type of sensor being used to measure temperature 3)What is action relay will take means to say where it is connected ?? to what it is connected.??

First Thank you for having patience. 1) between 15.5556 celsius and 18.3333 celsius 2) MAX31820 1-Wire Ambient Temperature Sensor http://www.maximintegrated.com/datasheet/index.mvp/id/8130 3)I wanted to use the PowerSwitch Tail II http://www.powerswitchtail.com/Pages/default.aspx

How you want to use below Item I wanted to use the Power Switch Tail II http://www.powerswitchtail.com/Pages/default.aspx Can you put in image file/ block diagram how actual setup look according to you

I'm wanting the arduino to trigger the powerswitch tail to energize thus turning on the freezer if the ambient temperature within the freezer has fallen out of the limits programmed.

http://forum.arduino.cc/index.php?topic=209691.0 THis link might help you solve your problem . They are using same Power switch

Devoidelk: I'm a homebrewer and wanted to automate some of the tasks such as keeping my freezer at the perfect temp, Shutting off a gas solenoid to maintain a boil, etc. I thought of getting a Arduino Mega 2560 rev3 with a temp probe and a power tail to control the freezer. My question, is that the route i would go for that or should I seek some other way to do it? I'm new to the microcontroller scene but i'm willing to learn.

If you're new to electronics and electrics, the powerswitch tail you mention is a nice way to safely encapsulate switching the mains. The setup you mention sounds quite feasible although the Mega sounds like overkill unless you're planning to add additional controls later.

Does this freezer lack thermostatic control of its own?

wildbill:

Devoidelk: I'm a homebrewer and wanted to automate some of the tasks such as keeping my freezer at the perfect temp, Shutting off a gas solenoid to maintain a boil, etc. I thought of getting a Arduino Mega 2560 rev3 with a temp probe and a power tail to control the freezer. My question, is that the route i would go for that or should I seek some other way to do it? I'm new to the microcontroller scene but i'm willing to learn.

If you're new to electronics and electrics, the powerswitch tail you mention is a nice way to safely encapsulate switching the mains. The setup you mention sounds quite feasible although the Mega sounds like overkill unless you're planning to add additional controls later.

Does this freezer lack thermostatic control of its own?

Yes, I plan to add more controls for pumps and stuff later. The freezer has its own control but as its for freezing stuff it cannot maintain the 60 to 72 degrees F that I need.

I am controlling a fridge using an LM335 sensor to detect the temperature and a breadboard Atmega328 to control things.

...R

Sounds perfectly viable. The only question I'd have would be whether the compressor would be upset by having the power yanked (effectively) when it was running. I don't know enough about freezers to know whether that's in any way different to what the existing controller does when it turns it off.

wildbill: The only question I'd have would be whether the compressor would be upset by having the power yanked (effectively) when it was running. I don't know enough about freezers to know whether that's in any way different to what the existing controller does when it turns it off.

Well of course, the power is always going to be turned off whilst the compressor is running - that is axiomatic. You cannot "turn it off" if it is not on! The thermostat turns the compressor on and off as needed.

There is one trick to this. If a compressor has just been turned off, it will have built up a pressure of fluid in its outlet system. This will make it more difficult to start and may therefore cause it to fail to start and thus overload. Generally, it has an overload cutout which will take care of this but having it happen is not desirable.

The control circuitry therefore should incorporate a delay of a couple of minutes after switching the compressor off to allow the compressed coolant to dissipate (you can often hear this happening in a refrigerator), before starting again even if the temperature (or other) criterion somehow suggests it should. This delay is often implemented in the start-up sequence so that if the system is manually turned off and on again immediately, it enforces the delay even though it has no "knowledge" of the previous state.

Paul__B:
If a compressor has just been turned off, it will have built up a pressure of fluid in its outlet system. This will make it more difficult to start and may therefore cause it to fail to start and thus overload. Generally, it has an overload cutout which will take care of this but having it happen is not desirable.

I have this problem with my fridge. Because it is powered from batteries and an inverter the fridge stops when some other loads are turned on (such as my netbook charger) and I have to leave the fridge off for about 5 minutes before restarting it. I do this manually because I haven’t figured out a simple means to get the Arduino to check if the fridge is actually running. Actually I now have LEDS in my controller board so I can see not to switch on the PC charger at the wrong time

…R

Robin2: I have this problem with my fridge. Because it is powered from batteries and an inverter the fridge stops when some other loads are turned on (such as my netbook charger) and I have to leave the fridge off for about 5 minutes before restarting it. I do this manually because I haven't figured out a simple means to get the Arduino to check if the fridge is actually running. Actually I now have LEDS in my controller board so I can see not to switch on the PC charger at the wrong time

Could you design a 555-based timer circuit to work as a pulse stretcher, so that when the compressor is switched off it is held off for five minutes?

The problem is that the fridge stops even though the switch is on. I presume the inverter is unable to meet the extra load instantly, the voltage falls briefly, the fridge stops and then won't restart because the compressor load is too high.

My Arduino code is already designed to leave a suitable delay between switch changes.

...R