PLCs/PICs (computer interfacing and controlling)

[ernie wrenn]

Augusta is the largest mfg'er of golf carts..... EZ GO and Club Car. I can check around and see if more are available (Used). They change them out when the carts are rebuilt.

Ernie

[g8rpi]

Hi Ernie,
Don't worry on my behalf, I've no turbines at the moment - no space :-(

Robert.

[jettoymaker]

Hi Guys,

Sorry the delay getting back, you know how it is

I was wondering Robert, given all that you say in your previous posts, that you would appear to have most if not all of the parameters and design considerations already developed to a point, so I was wondering if it would be possible to have a proof of concept/prototype produced for testing, based on these standing considerations, and if so, what else would I be able to contribute to facilitate a test piece?

The serial RS232 I am only just beginning to understand what it may do, although a USB adapter (FTDI chip) may be more conducive to "in the field" usage/adjustment. Programing it in C or PicBasic Pro, for me, could take a while...this is all beginning to enter the Black Arts level compared to the stuff I am familiar with.

Had a look at Ernie's idea and as a stand alone feature it would be a good idea indeed. Mine and John's problem is that we live in the nether world of supply (Australia) and so even a second hand unit here costs AUS$300 and up...I know: I checked out the three golf cart suppliers here in Melbourne. The most expensive one was AUS$750.

However, I wasn't aware of the hardware PWM on a PIC that Robert mentioned and would have to admit that it would make the starter integration for a system safer and more reliable, given the manual control aspects of the Curtis unit that will always still come into play.

Regards, Andrew

[g8rpi]

Hi Andrew,
I've actually built a PIC based unit a few years ago. It was built to provide "push button" starting of a RR Spey 101 in a boat project. I also wrote some code so it could be tested and demonstrated on my GTP-30. It also provided a serial data string to a laptop. I'll try to dig it out and post a couple of photos. An updated prototype is not a problem. One possible issue is that I don't currently have an engine to run it with. I can simulate all the signals though.

Robert G8RPI.

[ernie wrenn]

Robert...

Have you been holding out till we begged?

I also have several RR 201 and 522's... a couple of j-34's and numerous APU's and Huffers.

Sounds like that program would be perfect for crossover applications.

Ernie

[ernie wrenn]

Andrew

If you need any parts let me know and I will ship them to you via Post or UPS. I will scrounge for parts.

Ernie

[g8rpi]

Hi Ernie,
Didn't want you to beg. I just wanted a feel for the interest. As I don't have an engine myself at the moment, I don't want to put a lot of effort into something thats not going to be used. What have you got planned for the Speys?

Robert.

[ernie wrenn]

Just backups for the monent. The hearse is trying to eat my lunch. Everything ready to go a can't get a good start.

Talked to Fred Sibley Satruday and he advised a lift pump..... He said the J-34 fuel pump was not a lift pump but a booster and needed 28 psi intake to boost pressure to 240 psi.

Pumps are on they way. Keep you advised.

Ernie

[stimps]

So robert can you tell me where on the net i can go to start learning about how to program a PIC? Reason i ask is I am building an engine that is annular combustion chamber, reverse flow, and decided i want to control it using a pic. I am an electrician and have programmed simple instructions into PLCs before, so hoping i can migrate up to these smaller cheaper and more versatile option to the plc!! Id like to set one up to do the start sequence automatically.
I have ordered my PICkit 2 kit.

[jettoymaker]

Hi Robert,

John and I would be very interested in your proposal, although I don't know if I would be able to get my Mk. 1 Avon through the post for you to test on ;D

How badly would you need a test motor and what sort of test engine would you require?

With an updated prototype, would starter size and amp draw be something that would pose a problem, given amp draw currently required? I would assume the Spey test unit just triggered a relay and allowed the heavier starter circuit to deal with things.

Still have plans for the three Avons I have, so any starter unit would come in useful once I have a handle on the smaller stuff.

Thanks also Ernie for the offer to assist as it is always welcome...it's also reciprocal.

Think I have a simple start system to investigate for the moment, where we can use a couple of double circuit relays along with a simple resistor etc. and just feed in the required steps in current, as there are really only three current values we need to ENGAGE, START and MOTOR the thing, so no need to get more sophisticated for the moment, although, at a later date, a greater degree of control is going to be required and the simpler version will soon become redundant once further system refinement and service interaction becomes a necessity.

Sorry if I'm coming across ignorant as to process, but electrics, as I've said, is not what I do with any facility

Many regards, Andrew

[ernie wrenn]

I have several "Dial a Resistance" , for a better name for them, It is approx 14 inches long with 8 to 10 knobs for setting resistance levels needed. It will go WAY beyound any normal humans needs (except Chris...).

Where do you want it sent?

I also have boxes of 1% electrical components (gov. crap) from auctions. (resisters, pan pots, capicators etc if needed.)

Ernie

[ernie wrenn]

Take a look at this interface, looks like it handles most of the needed info..

E-bay #: 180417113406

Ernie

[g8rpi]

Hi Stimps,
Try Nuts and volts < www.nutsvolts.com > and ME labs < melabs.com > for some ideas. ME labs have a trial version of their PicBasic Pro basic compiler you can start with. If you are used to PLCs and have not done any "C" programing I'd recomend PBP. The very first task to try is to flash a LED. This makes sure everthing is working. You can advance from there.
Jettoy, I don't need an engine, it would just be nice. I've not got much done as I've been building some radiation detection gear that seems to be selling very well on ebay. The Spey uses an air turbine starter so the controller just has to turn on a valve. Controlling starter current can be done with contactors (large relays) and resistors or pulse width modulation (PWM) with a golf cart controller or similar unit. The PIC can drive any of these. The unit Ernie spotted on ebay is interesting. It would be usable as an insrument interface but could be a controller. I'll concentrate on the starter current control design for now.

Regards,
Robert G8RPI.

[stimps]

So i was wondering if there was any example code for a pic used in this way, and more particularly, which PIC is used to program for this application. Lets say, one that just monitors rpm and thetefore can control the fuel and start up sequence?

[g8rpi]

Hi Stimps,
Here is some code I wrote to read a standard tachogenerator and display % RPM on an LCD.

'25 Dec 2002
'Robert Atkinson
'Test software for pulsin to read GT tacho, 70Hz = 100%
'PBP 2.41, PIC16F84 4Mhz


'DEFINES------------------------------------------

DEFINE LCD_RSREG PORTB 'USE PORT B FOR RS SIGNAL TO LCD
DEFINE LCD_RSBIT 7 'USE b7 TO KEEP REST OF PORT CLEAR FOR MUX
DEFINE LCD_EREG PORTA 'USE PORT A FOR ENABLE lcd TO STOP MUX CAUSING PROBLEMS
DEFINE LCD_EBIT 4 'USE a4 FOR ENABLE

DEFINE PULSIN_MAX 41000 ' LIMIT MAXIMUM COUNT TIME TO 0.41S

'PORT ALLOCATIONS---------------------------------


IPP var PORTB.0 'INPUT PULSE FROM TACHO

'VARIABLES-----------------------------------------
RPM VAR WORD 'PERCENT RPM BASED ON 1/2 WAVE RECTIFICATION

PW VAR WORD 'ACTUAL PULSE WIDTH

'INITALISE PORTS-------------------------------------------------
PW = 0
RPM = 0

PAUSE 1000 'ALLOW LCD TO INIALISE


MAIN:

LCDOUT $FE,1, "RPM TEST V1.0" 'POWER UP CONFIDENCE CHECK
PAUSE 800 'TIME TO SEE LCD

lOOP:

PULSIN IPP, 1, PW

RPM = 35700 / (PW / 2) 'CALCULATION OF PERCENT BASED ON 2 POLE 4200 RPM = 100%
'35700 USED DUE TO 16 BIT MATH LIMIT
IF PW <400 OR PW >40000 THEN 'TRAP UNDER AND OVER PULSE WIDTHS
RPM = 0
ENDIF

LCDOUT $FE,1, "PULSE WIDTH ", #PW 'DISPLAY PULSE WIDTH 10uS RESOLUTION
LCDOUT $FE,$C0, "% RPM ", #RPM 'DISPLAY % RPM


PAUSE 200 'PAUSE TO SEE LCD
GOTO LOOP

END

Nothig great but it works ;-)