Newbie request

Russ,

          what you want to do can undoubtedly be done, perhaps using a Mega256.  However, the really serious concern would be one of the overall safety of the system.  In no way can an Arduino, Mega or any similar variant be used as a point of safety device therefore you would need some external method to shut down the system in the event of, for example an over heat situation.

Otherwise all of the items you mention such as controlling mains AC voltages, relays etc. can be done.  Similarly it is possibly to interface many sensors.  In respect of controlling potentially lethal mains voltages it is critically important that you understand the dangers of such voltages and how to work with them safely.

I would suggest you 'Google' such topics as using relays with Arduino's as there is a huge amount of information on the web and a similarly huge range of relay boards to build interfaces.  As a registered gas engineer I am familiar with flame rectification, I have never seen an Arduino application to do such a thing.

The basic arduino's are not really built for what amounts to, in your request, an industrial standard application in terms of the reliability and integrity of the control system.  This is a 'ruggedised' version of the Arduino that has better I/O protection than a standard Arduino.  I hope that helps and I am sure some of the other experts on E14 will offer some good advice.

Very good points. I would like to add that this is more of an issue with an Arduino / Launch Pad or any other development / evaluation board. It is not the uController on board but the minimalist design of the board that is the issue. All the uControllers can be coded to be fault tolerant using watchdog times and the like. It is issue as already stated such as protecting the inputs to the uController from noise and damaging spikes induced by other powered equipment and now knowing Bob is a gas Engineer he will understand this, the controller also has to limit the power going to the hazardous areas leveraging "Isolation barriers" or similar approved technology, this is where 4-20mA loops for instrumentation come in, the remote instruments are powered by the loop and also control the current through it up to that limited by the barrier. there are loads of rules and regs when it comes to this stuff (Not to scare you but you need to be aware of the local regs)

For full disclosure in my former life for several years I designed and installed industrial control systems with remote control for Northern and Southern Gas to control the distribution of gas throughout the regions of the UK, everything from a bar to thousand PSI 20M cubic feet underground storage... Ahh those where the days

Thanks Peter and Bob for your prompt replies. Chuffed to bits! Don't worry guys this project is not for public consumption, just fed up having to do everything manually so thought i might try to automate things a bit. Have been in both aero and auto engineering for last 35 years so have a reasonable respect for safety. Not a programming or electronics expert but not an idiot either and willing to learn and experiment with a little help from those in the know.

Well it seems that Pandora's box has been well and truly opened. Let me give you the sequence of what I am attempting and then I will give an idea of components.

The set-up relies on a Babington burner which basically remains alight with a compressed air source as long as fuel (waste engine oil at approx 60 C) flows across a brass ball. No fuel, no flame.

Power for the heater control is via a master switch (220v 30A a/c) in series with a water thermostat set to a max of 50C (to prevent Coprax pipework from undue heat). Have sourced stat with 3 degree threshold to prevent too rapid on/off cycling. Output power is then supplied to an oil pump, a compressor (with own pressure cut-out) and to a stat controlled immersion heater in series with a level sensor (to prevent heater running with no oil). This preheats a small amount of waste oil to 60C. Once the oil reaches this temperature I require the controller to operate the pool circulation pump via the contractor relay already present in the pump control electrics. The next stage is to open the oil solenoid valve (NC) to allow the hot oil to flow into the burner but only if the flow switch registers a positive flow (to prevent static water boiling in the pipework). When the hot oil flow has purged the lines (after about 60 seconds) I require the controller to open the air solenoid valve (NC) and the igniter to operate for 15 seconds. If the flame sensor registers the burner is alight everything stays as it should until the water reaches it pre-set temperature and shuts of the power. I also need the flame sensor to continually monitor the flame. In the event of a flame out I would like the system to attempt to relight the burner 3 times as long as all parameters and conditions are met again after which it registers a fault and requires a reset. (not sure if this is possible). I know that several relays would be required and have seen relay modules available for use with Arduinos. I realise that there are some inductive loads that may well be in excess of current limits of these relays so would use higher capacity SSRs switched by the relay module. I presume the specs for these relays are higher for purely resistive loads? Could i just desolder these relays and use the switching circuit of the controller to activate the SSRs? Most of the components have quite small electrical loads save for the 1.5 kw heater, the oil pump. These loads however can just be controlled via the master switch and subsequent relays without the need to over complicate what the controller has to do. Hope this gives a better insight into the project.

I look forward to seeing the plans and helping where I can, it looks to be a reasonably challenging project

Good luck

Peter and all,

I have been doing some more research and perhaps the Arduino/Pi options may not be stable enough for the application. In light of this I am considering perhaps using a Siemens Logo! PLC to perform a similar function. It seems relatively straightforward using their software to program with perhaps some add-on modules to expand the inputs/outputs if required. It seems to me that controls over noise etc are dealt with internally by these units. Does anyone have any experience using this type of equipment and should I be addressing a different part of the forum? Any help or assistance greatly appreciated.

your choice will certainly provide for a more rugged and reliable project as most of the PLC are designed for this kind of thing, just get the right modules for each kind of load or sensor

I used to design systems way way back with Omron and Westinghouse PLC's, sot sure how much they have progressed since then but I would imagine the basic principles are the same

Robotics Topic may give you some good advice

your choice will certainly provide for a more rugged and reliable project as most of the PLC are designed for this kind of thing, just get the right modules for each kind of load or sensor

I used to design systems way way back with Omron and Westinghouse PLC's, sot sure how much they have progressed since then but I would imagine the basic principles are the same

Robotics Topic may give you some good advice