Has anyone ever used a plc to??

[mer]

Some might say this would would or might be a dum question but has anyone ever used a small 12/24 volt plc for a ignition system for a engine .......

 

[TConnolly]

What kind of engine? If it is one of those really large low RPM engines like the ones used on ships (that do only a couple hundred RPM) a PLC could probably do it - though I'm not sure if those even require an ignition system. But no way is it anywhere near fast enough for the high reving little four banger in my Toyota. Why would you want to use a PLC?

 

[Fred Mau]

Most engines on ships, assuming they're not gas turbines or nukes, would be Diesel and wouldn't have an 'ignition' system anyway.

But I agree - no way a PLC would be fast enough to do ignition. Figure a V8 engine at 3,000 RPM - that's energizing the coil 24K per second, or once every .04 milliseconds (do i have my decimal right? it's too late in the evening)

Even if you could get a PLC to scan that fast, which you can't, the timing - so many degreess off top dead center - probably wouldn't be anywhere near as accurate as need be.

 

[Paul B]

Firing the outputs that fast would result in an unacceptable MTBF.

 

[JRW]

If your serious about a PLC controlling this-
Look at the Siemens FM352-5 high speed boolean processor

http://www.automation.siemens.com/m...0/function-modules/FM352-5/Pages/Default.aspx

 

[Mickey]

But I agree - no way a PLC would be fast enough to do ignition. Figure a V8 engine at 3,000 RPM - that's energizing the coil 24K per second, or once every .04 milliseconds (do i have my decimal right? it's too late in the evening)

Even if you could get a PLC to scan that fast, which you can't, the timing - so many degreess off top dead center - probably wouldn't be anywhere near as accurate as need be.

I'm not buying the math. Keep in mind i am NOT a mathematician .

A four stroke V8 only has 4 firings pre revolution so

3000RPM=12000 firings per minute=200 firings per second

That's 5 milliseconds
I don't think a PLC's scan time is consistent enough to it it though.

 

[Fred Mau]

Yeah, you're right. I forgot about the 4-stroke part and I confused seconds and minutes. Like I said, too late in the evening.

But, yes, even if you could scan that fast it wouldn't be steady enough.

 

[Paul B]

If your serious about a PLC controlling this-
Look at the Siemens FM352-5 high speed boolean processor

http://www.automation.siemens.com/m...0/function-modules/FM352-5/Pages/Default.aspx

J - that link doesn't work for me.

Here is one:
http://www.plctalk.net/qanda/showthread.php?t=10857

 

[TConnolly]

Most engines on ships, assuming they're not gas turbines or nukes, would be Diesel and wouldn't have an 'ignition' system anyway.

I wondered about that, wasn't sure if an ignition system was required or not since most marine diesel uses low grade bunker C fuel oil.

 

[mer]

ok!!!!

ok i admit it was a dum question i was just looking at a encoder that would operate at 9000 rpms then looked at at high speed counter that would operate at 5khz and thought that it would be possible but as far as keeping up a plc could read the info at high rpms its the outputs that are to slow correct??? ive had dumer ideas that lead to workables...

 

[shooter]

the only way to do this is trigger on the 0 point of the flywheel and then use analog timers (like 555) and put the resistor in your didgital diagram. that could be a plc.
that way there is a good possible shift however it takes time.

 

[Mickey]

ok i admit it was a dum question i was just looking at a encoder that would operate at 9000 rpms then looked at at high speed counter that would operate at 5khz and thought that it would be possible but as far as keeping up a plc could read the info at high rpms its the outputs that are to slow correct??? ive had dumer ideas that lead to workables...

Don't be discouraged by a bunch of know-it-all's on the internet.( notice I to said it would not work)
Go for it. I'm sure there are others here that have done things for the intellectual exercise, knowing full well it has no real world or commercial value.

 

[mordred]

Guilty of that myself.

 

[JRW]

Mer

The FM352-5 is a FPGA that you program in a ladder logic.
It has a scan of 1 microsecond, yes micro.
Check out the link in my previous post.
The link works

You ever see cigarettes being made?
This bad boy is used for this. Just one of many applications.

 

[nathan.slade]

A plc is not fast enough. Please. What is the thing that controls the motor in any modern car? Does it have inputs? What about outputs? may be some control in there. Any of this sound familiar?