help needed constructing a homebrew water bath

[gonadgranny]

Hi all. I am attempting to build a simple water bath for keeping chocolate melted (and possibly for sous vide cooking) and am wondering which microprocessor would be the most economical to buy. all it needs to do is take a temperature reading every now and again so it doesn't require a fast clock speed and the program its self would be pretty simple i would imagine (IF temperature < 50 switch on heating element ELSE switch off heating element) type of thing. i have used an arduino before and found it to be most accommodating but am not averse to trying my hands at another system and language as long as it is well documented so i can figure out how to do what i need. one last thing, i would like to know which is the safest way to heat water with electricity. i dont want to inadvertently fry myself with this project and the thought of water and electricity give me the heeby jeebies but if i can garantee a safely insulated element then it should not be a problem. would you imagine something like this to be a good option? thanks very much in advance for any help. Danny

 

[milan.rajik]

Hi

As you have used Arduino it would be better if you can use Arduino Nano v3 or Mini Pro 5V type. You just need to connect a LM35 sendor to A0 pin and a BC547B transistor to any digital IO pins like D2. The transistor will drive a relay which will control the heater.

If you need to use AVR or PIC then you have to find the smallest controller which has atleast 1 adc channel and runs on internal oscillator.

 

[gonadgranny]

cheers for the reply mate. ive just ordered an arduino uno off ebay.so cheap now! if anyone could let me know whether using a few of these to heat the water would be safe i'd be very grateful. cheers.

 

[milan.rajik]

You can buy UNO R3 and Mega2560 or any Arduino boards from Banggood.com They are really cheap there. It is around 7.5 USD for UNO R3 and 10 USD for Mega2560.

Yes, you can use such an immersion heater but make sure it is of good quality. The heater coil inside the element needs to be properly insulated. Don't go for cheap thing.

 

[ArticCynda]

Isn't an Arduino overkill for this application? I believe a potentiometer, thermistor and an opamp as comparator (with positive feedback for hysteresis) would pull down your BOM cost significantly. With the opamp output you can then directly drive a relay to enable or disable your heater resistor.

 

[BradtheRad]

if anyone could let me know whether using a few of these to heat the water would be safe i'd be very grateful. cheers.

500W. I have one about this size. It gets a mug of water boiling in a couple minutes.

Notice your range of water level is an inch or so. It probably has a warning against submerging the plastic handle. You'll need to construct a jig to grip it and hold it the proper distance down inside the water bowl.

The 1000 W heater can handle a larger range of water level. The photograph shows it with a handy tab on the handle which fits over the edge of a bowl.

 

[gonadgranny]

Notice your range of water level is an inch or so.

What exactly do you mean by the range of the water level? I was thinking of buying 4 of the elements and arranging them as evenly as possible. Presumably one can simply leave the elements switched on for longer to heat a larger volume of water? ArcticCynda, thanks for you help but i have ordered the Arduino now. It only cost me £5 and I am familiar with it.

 

[BradtheRad]

What exactly do you mean by the range of the water level?

The water bath can be any depth you choose. You will immerse the unit until almost all the metal portion is covered. Subsequently the water can be allowed to drop an inch or so. Then the loops will become exposed to air.

The instructions warn that you should not operate it without it being immersed.

 

[gonadgranny]

You will immerse the unit until almost all the metal portion is covered

I thought that you would be able to immerse the whole thing in, plastic and all due to it being insulated....? I've ordered some now so i'll check the instructions and post back. Thanks again for the help folks.

 

[milan.rajik]

The plastic part should not be immersed. If the plastic handle of the heater is moulded type then you can immerse it but I have never seen moulded type and so there will be gap in the plastic part and if immersed in water you might get a shock.