What PICAXE and hardware do I need?

[brksb46041]

A little background: I have a diesel vehicle i have converted to run on waste vegetable oil, in order to do this i have to start and shut down the engine on diesel, then switch to veggie oil (stored in a seperate tank) once it is heated to sufficient temperature (by means of a heat exchanger in the tank and engine coolant). Right now the setup appears very crude because i have analog gauges and SPST switches mounted in random locations in the truck.

Basically what i am wanting to do is use a PICAXE to display on a 2x16 or
4x20 LCD the temperature, fuel level (in numerical gallons or, maybe a bar), and status of the system (whether it is running on diesel or veggie oil). I would also like the PICAXE to trigger the Pollack valve (valve that switches tanks) when it reaches a certain temperature.

Seperate from this PICAXE, i will have a master switch toggle switch that will allow me to arm or disarm the system (for short trips).

The fuel sender is a 12v, 240-33ohm unit and the temperature sender is a normal 12v unit used for coolant temperature on many GM vehicles. I'm not sure what the resistance readings are on the temp sensor are but it can be switched out for another unit easy enough.

I have done some programming using Matlab so am familar with program operators but i have zero experience with integrated circuits. As you can imagine i have many questions.

Can this be done with one PICAXE?
Should the LCD be serial enabled?
What other hardware is required?

Thank you in advance for any help, i am looking forward to getting some PICAXE parts here soon and beginning to tinker.

 

[Dippy]

Firstly, I'm basing this on your description. You can see your project, I can't. But yes this can be one with PICAXE plus accessories.

The LCD is easy. How to use it has been covered a zillion times on this Forum and people will help. Serial/Parallel. For alphanumeric LCD I'd stick to parallel myself, but it's a personal thing... For graphic GLCD, deffo serial.

PICAXE has ADCs, so with some extra components it will be able to read your senders. I'm not sure whether your temp sender is current or voltage based to the gauge, but it can be done.

The outputs of the PICAXE can control a transistor/relay circuit to switch things on or 'over' depending on your requirements.

And it could probably play a tune while it's doing it.

To keep the doom&gloom brigade from wetting themselves you must also ensure that the power supply to the PICAXE is well regulated and spike suppressed and fused and that in the event of failure the circuit will fail safe. And that you have a 'master' override.
Remember: PICAXE will require a smooth and spark-free 5V DC.

And please fit your final doo-dah in a nice tough (ideally screened) box and not some tatty old bakelite pot from Grandad's radiogramme.

 

[hippy]

A PICAXE-18X would seem most suitable to me.

That has a large program memory and enough output to drive the cheaper parallel HD44780-style LCD's directly with two lines left for controlling the valve, LED or piezo sounder - an extra 08/08M/14M/20M can be used if more outputs are needed.

It also has five digital inputs ( of which three can be analogue ) for your master and other switches and temperature / level sensing etc.

 

[brksb46041]

Thanks a lot for all the help, just put in my order for an 18x, board, 16x2 lcd, and a few 7 segment leds. Now if i can just figure out the code....

 

[inglewoodpete]

Lots of bedtime reading while you're waiting for the order to arrive....
Manuals 1 (getting started); 2 (commands) and 3 (interfacing)

And, of course, read and observe the forum for the problems others are having.

 

[demonicpicaxeguy]

have you got any photos of this conversion, i'm going to do the same thing later on in the year

 

[moxhamj]

What a great project. Even though no-one may have built this exact setup, between us we have working boards and code modules for all the parts you will need. So yes, it can be done, and also, yes, with the help on this forum we can get all the parts working.

Here in Australia diesel is $1.69 a litre and the word on the street is that waste vegie oil is 15c per litre. Plus instead of diesel fumes you get a nice whiff of fish and chips as the vehicle goes past. Or so I am led to believe.

I agree picaxe 18X to start. It is the minimum chip that can run a display. The display does tie up 6 of the 8 output lines and you might run out of outputs. There are a few options and I'd suggest you get the display working first, then maybe look at a second 18X board to do all the sensing and control. The boards can talk to each other via serial links and this could be just one wire as the sensor board could send all the data to the display board which puts it up on the display.

The boards will need to be programmed a few times as the project evolves so the programming socket needs to be easily accessible.

If you can get the display working, then get a sensor reading something and then control a relay, all the hard parts will be done.

I have a picaxe controlling my car radiator fan at preset temperatures and it works fine (the original controller stopped working).

Keep the questions coming - this forum operates 24/7!

 

[Diesel62]

A word of warning .Do your investigation into the vege oil carefully , we see lots of attempts at saving money costing thousands on injection pump repairs.

 

[Dippy]

Maybe this is why we haven't heard back on this project?
... he's broken down in the wilderness with a Potato Chip stuck in his injector.

 

[slimplynth]

chippy's taxi

my mate Dave runs his Ford transit van on pure vegetable oil, with a little Meths for flavour.. has been doing it for a year or so. I've read that it will eventually coke up an knacker up the insides but its an old banger anyway.

He has no pre-heater for the veg oil, theres a youtube video showing some lads doing tests on this, they monitored the temperature of the injectors, entry and exit and showed the temp was easily enough for the veg oil (on a warm day) to get to the right temp.

That said, the price of veg oil is almost the same as diesel in the UK now, price has sky rocketed in the past year, wonder why?