Hello all,I'm new to Arduino, but have worked with Basic Stamps and some MikroBasic programs. I'm looking forward to sitting down and learning everything. I just don't have time for this one...I've just ordered a Uno and LCD/button shield from adafruit for a project I need finished right away...The task is to heat a big tub of solidified oil to get it to melt slowly for further packaging. If it is heated too fast, the product around the heater element burns and spoils the whole batch.I'm basing this on the Sous-vide project, it seems like it has everything I need (almost)http://learn.adafruit.com/sous-vide-powered-by-arduino-the-sous-viduino/the-whole-enchiladaThe only problem is that it looks like it will bring it up to the setpoint temperature, but with no regard on how fast it does this.Can someone advise how you would limit the intensity of the heater in this sketch? In a perfect world I'd like to have a pot that would increase/decrease the duty cycle inside the PID loop - thus slowing the heating cycle.I will be using an SSR and not a mechanical relay if that helps/matters.
You do not need to use a PID when you are talking about volumes such as this... ...Solid State Relay with Zero Crossing support built in. What size element do you have ?
The element is 4500 watts, It's big, and I could use something smaller to get the oil to warm more slowly, but at the end of the cycle I need all 4500 watts to get it super hot.
Have you considered two elements?
What you want to do it turn the element on and off many times per second to essentially lessen the power that it is outputting. You will have to experiment with this to find the appropriate numbers.
Quote from: radman on Aug 14, 2013, 05:20 pmHave you considered two elements? This seems right to me. What type of heating element are you using? What's the surface area of the element? How hot is too hot for the fat?
QuoteWhat you want to do it turn the element on and off many times per second to essentially lessen the power that it is outputting. You will have to experiment with this to find the appropriate numbers.I have some questions on this;What effect will switching 4.5kW, which is quite a large load, rapidly like this have on other electrical equipment in the area? Will switching affect the lifetime of the element?How would the element temperature vary with switching frequency?
Essentially - the element temperature will be halved if you switch at 1/2 the frequency of the mains
The temperature rises in accordance with the increase in the surface loading (watts density) and has a detrimental effect on the life of the element.
a resistive style heating element (i.e. hot water service) has the same density of heat in an element - they just vary the length of the element - thus adding additional elements will allow the unit to come upto temp more quickly but will do nothing to alleviate the initial issue.
What type of heating element are you using?
The op has not said what Country he is in