PLCs/PICs (computer interfacing and controlling)

[Richard OConnell]

I'm doing some price shopping on Programmable Logic Controllers that would be able to interface with a TAC generator (tachometer) and some standardized computer slot (like PCI).
I also need another that will be able to pick up a resistance sweep coming from a thermal sensor.
Lastly, I just need a few I/O PLCs (or one with multiple inputs) that can just detect boolean values (True/False connections) and send low amp current out to trip relays.

I also need a sample of code that gives me an idea on how that specific card is accessed through a programming language (preferably C++ or VB.net).

Might also go with RC controllers if it looks do-able, but I really need a way to interface an engine with a computer.

[g8rpi]

Hi Richard,
Are you looking for a PLC or interface cards for a PC? Its quite a confusing area. Basically a PLC (Programable Logic Controller) is a self contained device that monitiors and controlls a system. While they may be programmed from a PC and might send data to one, they don't need a PC to work. They were originally designed to control simple repeditive industrial machines and replaced pneumatic or mechanical sequencers. The advantage is that they are stand-alone and don't need a PC once they are set up. Downside is cost. The units arn't cheap and some manufacturers charge (a lot) extra for the programming software. PLCDirect <http://www.plcdirect.eu/en/> do some lower ost units. Interface cards plug inside a PC and provide an interface to the outside world. you then write your code in C, Basic, Vee, Labview, Simulink or whatever. This is great for monitoring but if you are ccontrolling a turbine you need the PC to run the engine. You would typically need at least two cards plus additional interface circuitry. There are a couple of in between options. one is a industrial PC carddesigned to run a minium system. One standard for this is PC-104. Interface cards just stack up on the base. can be quite costly. Lastly (and my personal preference) is to use a microcontroller such as a Microchip PIC. These need some electronic hardware construction, but are cheap and versatile. They can be programmed in C or Basic as well as low level assembler. I've used a PIC 16F877 to provide a fully automatic start secquencer and protection module. This also sends status, temperature and speed data on a serial port. This data can drive a display or a PC (or both at once. It is programmed in ME Labs PicBasic Pro < store.melabs.com/prod/software/PBP.html > they have a restricted demo version. The unit I built has been used on a Garrett GTP 30 and a Rolls Royce Spey with minor changes in code. If there is interest I could design and make a general purpose controller board based on a PIC.
Robert G8RPI.

[Richard OConnell]

Thanks for the reply,
I'm actually looking for one that DOES interface to a computer. At this time I probably wont be actually controlling the engine from a computer, but I intend on putting a computer and screen inside a vehicle and write a front-end program in C or VB with visual effects.
The Microchip PIC sounds like about what I need, so I'm going to do some more research on it. Thanks for your help!

[g8rpi]

Hi Richard,
Let me know if you need any PIC bits or advice. Maybe we should move this to projects and see if there is any interest from others. This is just the sort of thing a PIC is good for. My design just sent an ASCII string out of the serial port (USB is also easy) with the current data. You can just monitir it with a terminal or use a C / VB program to make a fancy display.

Robert G8RPI.

[jettoymaker]

Hi Robert,

I'm working with John on his 10/98 project and would like to discuss PICs. Would you be able to enlighten me?

[g8rpi]

Hi,
I can try to enlighten you :-)
My thoughts were that if there was enough interest I could design a general purpose Pic based controller / interface. It would act as a simple start sequencer and protection unit and or interface to a computer or display. It would be supplied programmed with basic controller that just needs configuring with limits and time delays. Alternatively those who want can program it themselves in C, PicBasic or assembler. It would monitor engine parameters and drive relays to operate fuel pump/valve, ingnitors and starter. It would have a serial port to drive an LCD dispaly or/and PC.

Robert.

[jettoymaker]

:-/Thanks for the response Robert,

At the moment John and I are putting everything in a new motorcycle and improving things above the previous proof of concept bike I worked on with John, that you would have seen on You Tube. For the moment the main priority is getting the start to be a little less busy, as you would have seen John's juggling act on the latest engine's start-up. My particular problems are concerned with the throttle application for the bike, in as much as I am trying to adapt a standard 12 volt motor controller to control pump rpm for throttle control. Once I get that organized, the big problem is control and monitoring the engine, pressures and temps, along with display interface and rider inputs. Will a PIC handle these types of aspects or would a PLC be more in tune with the rider/bike/engine requirements?

[jettoymaker]

By the way, sorry the emoticons in the previous reply as I'm still getting used to forum format and what is where

[g8rpi]

Sept 14, 2010 1:32:51 GMT -5 jettoymaker said:

:-/Thanks for the response Robert,

At the moment John and I are putting everything in a new motorcycle and improving things above the previous proof of concept bike I worked on with John, that you would have seen on You Tube. For the moment the main priority is getting the start to be a little less busy, as you would have seen John's juggling act on the latest engine's start-up. My particular problems are concerned with the throttle application for the bike, in as much as I am trying to adapt a standard 12 volt motor controller to control pump rpm for throttle control. Once I get that organized, the big problem is control and monitoring the engine, pressures and temps, along with display interface and rider inputs. Will a PIC handle these types of aspects or would a PLC be more in tune with the rider/bike/engine requirements?

[g8rpi]

Hi All,
Sorry about the odd posting, something was funky with the Forum. I kept getting logged off.
Anyway, I'm not sure what bike you are talking about, do you have a link? A PIC is perfctly capable of monitoring the engine, sequencing the start and driving a display. A PIC is also fully capable of providing a PWM output to control a pump's speed and provide throttle control. I would use two PICs, one for the throttle, the other for monitoring. Where are you located?
Robert G8RPI.

[Morkai]

I agree that PIC is the way to go. That's what I plan to use for my ECU, working with PIC's is another of my hobbies. Isn't it great when you can combine one hobby with another? They will do pretty much anything you want, but there are many different chips with different specs (memory, i/o, etc) I have probably half a dozen different type PICs for the various projects I want to do with them. If you plan on doing your own development, I would suggest a demo board for prototyping. I have the QL200 you can find on ebay. It helps in development a LOT, plus it has a lot of example code for controlling the different interfaces. Using the LCD displays is quite easy.

Maxim has a lot of good chips as well, such as the MAX6675 K-type thermocouple to digital converter chip. Both Microchip and Maxim should allow you to order sample chips as well.

I'm also working on a tach interface to allow the PIC to drive one of the common %rpm av tach gauges you can pickup online. (I like analog)

[jettoymaker]

Hi Robert,

Sorry the delay in replying...not enough time in the day ;D

The bike in question is the one built by racketmotorman. See link below.

www.youtube.com/watch?v=q_MRUxWEOZ0

We spent many long hours and not a few difficulties getting it to do what John got it to do. We lovingly call it "Frank", short for Frankenstein.

I unfortunately live the next state over from John, so the 12 or so years of R&D on the subject of Jetbikes has been very long distance...but John makes it all very possible.

I can't begin to overemphasize the level of electronics' ignorance I contain, so I would need a large amount of basic instruction on what a PIC is and what to do with one (or several). Would you be so kind as to point me to a basic source of PIC for Dummies or something of that sort, as I don't wish to drive anyone mad with my first attempt at an understanding of the subject.

I would feel a lot better asking you any further questions after a little study.

Regards, Andrew

[ernie wrenn]

Class for PLC Dummies:

I am in. Where do we sign up.

I would love to have a PLC help with startup and get readings. We have a computer from a Police patrol car, with 80 gig hard drive, running windows, with touch screen.

Ernie

[g8rpi]

Hi, Sorry for my late reply. Been very busy at work and now have a head cold so forgive me if this makes even less sense than usual. Not sure I can help with PLCs. I have used them but not a lot. For small projects I've found PICs to be better. I'm not a great programmer, but there are some $50,000 machines out there with my PicBasic Pro code in them ;-). I am good at the interfacing circuits though. For bevelopment programming I'd recomend Microchips PICkit 2 Debug Express, stock No DV164121. For $50 this gives you a programmer and a prototype board with a PIC16F887 (44pin). < www.microchipdirect.com/productsearch.aspx?Keywords=DV164121 > The programmer can also act as a 3 channel logic analyser, pulse generator and timer. Not bench kit, but VERY usefull if you don't have an oscilloscope. It does not have an LCD but these are cheap and you may as well learn how to connect it up. You can also choose your own port(s) for the LCD. For Software, I highly recomend ME Labs PicBasic Pro. Not the cheapest, but reliable with good support and low cost updates for life. They also have a free verion that has a limit on program size but is adequate for many projects. < melabs.com/ > . On Ernies comment on Tachometers, are you talking about driving a typical electromechanical aircraft Tacho indicator or an electronic one? The electromechanical units normally have a "Drag-Cup" (or disk) and can be very unreliable. They also need a 70Hz 3 Phase power signal to drive them. One of the motion control type PICs could do this but it seems like a long way round! I'll try to get some beginners PIC links together.

Robert.

[joe0545]

Hi All , first post here ,
I have done a lot of plc work almost exclusively with Siemens products,
heres a link to a you tube vid of a setup i made to monitor the essential rpm / temp etc ,

www.youtube.com/watch?v=MFkIeCqskds

This could have been expanded considerably to include start up sequencing etc but as it was just a backyard test with no intentions of mounting it on some vehicle or the other it was not necesary,

This setup was using an S7 200 series plc , v good but these are costly along with the software and other interface components /software/hardware,

However there is a very good package that siemens sell called LOGO,
There is a starter pack with instructions and software and I see they now even offer a kit with a TD display ,

Dont know if anybody will be interested in this but their stuff is pretty user friendly and you dont need a degree in electronics to be able to get something up an running ,

Heres a link to a supplier in the UK but siemens do have worldwide presence , and theres lots of forums and blogs where one could get further help ,

uk.rs-online.com/web/499835.html