john banks

http://www.national.com/ds/LM/LM555.pdf

See here for 555 datasheet and consider the monostable circuit.

http://www.jaycar.com.au/PDFS/relaydrv.pdf

See here for a primer on driving relays - note the PNP example will take the active low outputs from the LM3914N circuit of the Knocklink. Note also the 555 timer can source or sink 200mA.

So some questions:

1 - how much current does your WI trigger relay draw?
2 - do you switch the positive or ground supply to the relay or does it not bother you?
3 - do you want the WI to trigger just while the Knocklink LED is lit or for a delay?

http://www.national.com/ds/LM/LM3914.pdf

Here is the datasheet for the chip that the Knocklink uses.




Note the Knocklink chip at the top. The very top line of the PCB carries +V, and the top row of connections on the LM3914N grounds the other side of the LEDs. This is where we can take our active low logic signal to interface to transistor or 555 to drive your WI relay. Choose the LED you want to activate on.

Does the Knocklink light them in a row or just individual LEDs? It depends on whether pin 9 of the chip is low or high and I can't tell from the pictures - ie is it bargraph or dot mode?

To drive a logic input we would need to use a pull up resistor, so it might be better to use one of the 10 spare LED pins- could be one in between two of the LEDs?

Lots of ideas for you!

[Edited by john banks - 3/14/2002 6:20:10 PM]

Cosie Convert

1 - I will measure it

2 - Ground

3 - I have my own latching circuit which will hold the W/I on whilst the boost pressure switch is made.

The Water Injection, once called for by the K/L, will be required whilst on boost. This is due to the charge temp rise caused mainly by heat soak of the intercooler, turbo, manifold and pipework. It is normally only 4th and 5th gears it is required.

I'm making up a charge cooler at the moment which will help keep this under control..........which is exactly what I need to run more boost

thanks

Andy (away to digest 20 pages of pdf file !)

(40 pages now !!)

[Edited by Cosie Convert - 3/14/2002 6:27:00 PM]

john banks

I suggest this then. The logic is all sorted so that when the LED is lit the first relay will operate.

I think using this setup will be good as it will not load the LM3914N, and the 555 will not get upset by your switch and latching circuit.

What do you think? Need a miniature PCB relay that takes less than 200mA for the coil but will pass enough to supply you WI relay.

Cosie Convert

This looks the business john

The relay driving my W/I is a standard automotive 30 amp job, I would be surprised if it pulled more than 500ma but I'll check it anyway. It may even be under 200ma

The knocklink climbs in bar mode, do you know which pins are used for LEDs 1 to 5 ? I would like it to energise either ON the first amber or better, between second green and amber which could be done if they use alternate pins. That way I should never see an amber !

Would I be able to use the same system for a buzzer on the big LED (can't call it big red or it wakes up T/Pete) Just as an "Out of water" alert or a hot summers day "Too much fun" alert

Andy

john banks

We could use a 556 timer (pair of 555s in IIRC a 14 pin DIL package). Use one channel for the relay, the other for the buzzer - just use a buzzer within the power levels of the 556 - should be easy - don't need another relay - just connect directly.

Will need to have a look at your Knocklink at Knockhill to see which LED pins it uses.

In the words of Big Red himself,
l8r m8.

[Edited by john banks - 3/14/2002 9:04:22 PM]

Cosie Convert

Looking at the pic, you can just about make out the tracks behind the board, looks like pins 18 16 14 (presume 12) and 10 are used.

If this is the case, then I can use 15 for the W/I and 11 for alarm warning.

Also may use pin 1 as a "must try harder" prompt

john banks

Must try harder = connect to "Nitrux" pro pro pro solenoid

Cosie Convert

Don't tempt me. My old car which I sold last year is sitting in a garage 10 miles from here with a full Nitrous bottle and 2 stage injection kit

JB Did you ever work out if a thermocouple output could be modified and processed via a LM3914N ?


Andy (Today building a flashing LED circuit..... tomorrow an ECU with anti-lag, traction control, yaw control, active diffs, gearshift, fly by wire throttle, matter/anti-matter reactor.... etc )

john banks

Yes I did, posted it in the earlier thread, but not got around to building it yet. There is a cheap IC which converts the K-type thermocouple output to a level suitable for a DVM or LM3914N.

There is one issue with the 555 circuit - I don't know how low the output of the LM3914N is pulled when the LED is activated - it has to be <1/3 of supply to the 555 - so under 4V. I think there is a resistor in the LM3914N to regulate the current. Need to look into this issue a bit more and probably measure it. Is one LED lit all the time on the Knocklink? Can you light some up (green ones are OK ) and measure the voltage at the output pin compared with ground? If it is under 4V we should be fine, if not will need to think a bit harder. Can't think of any other issues with the circuit - normally I think of loads, so one is not too bad

T-uk

andy,

did a guy mail you about some Subaru 4pot brakes he is selling?,told him you might be interested,they might not offer enough stopping power,for your 350bhp though.

john banks

Ignore this it was a crap circuit

[Edited by john banks - 3/15/2002 5:36:28 PM]

john banks

Ignore this it was a crap circuit too

[Edited by john banks - 3/15/2002 5:38:00 PM]

Cosie Convert

T uk - Yes thanks , he did. I am however going to hang on and go for AP's if I keep the car long enough ??

thanks anyway


JB - I was just about keeping up with version 1 ! Now you're starting to mess up my brain

Can you point me to the thermocouple thread please, I think I'll start with a simpler project just until I get a feel for it

thanks

Andy

john banks

Sorry I have a nasty habit of doing that. Just exploring all the options. It seems that the LM3914N may be able to directly drive a low power reed relay which we then use to drive your relay.

Part of the problem is you are switching the ground AND want to power the relay when the LM3914N output is low (=LED on). This is a bit of a combination for a simple solution. I think the 555/556 design would work also, and I don't think the 4V issue is a problem. Please don't be put off I am sure we can get it working!

http://www.scoobynet.co.uk/bbs/threa...threadid=71958 is the stuff on the thermocouple display project.

[Edited by john banks - 3/15/2002 5:39:03 PM]

Chris.Palmer

CC,

I'm in the process of building an EGT guage (may be using LEDs - pref Digital Display) -

For Inlet Temps its worth looking at the National Semiconductor Ics LM34/35 & LM334/335 - good for up to 150 C - Application Note 460 for the LM34/35 gives an example cicuit using a LED bar driver.

For EGT temps I think I'll be using an Analog Devices IC AD594/595 which is more accurate at higher temps.

Hope that helps.

Ps - Would be interested to hear from anyone thinking of producing their own Knock Guage, as this will probably be my next project.

Cheers,

Chris

[Edited to say]

DOH - beaten by the John - Again -lol


[Edited by Chris.Palmer - 3/15/2002 4:34:51 PM]

john banks

Application note 460

john banks

AD595

Sorry Chris

Don't you think the AD595 circuit looks easier?
the two components being for surge protection for the paranoid

You can get the AD595 from either Farnell or RS in the correct package cheaply in small/single quantities.

Knock gauge - I was going to have a "closer look" at Andy's Knocklink

[Edited by john banks - 3/15/2002 4:41:26 PM]

Chris.Palmer

John,

You're right about the simplicity of the Analog Device IC - all the work is done for you. The National Semiconductor ICs require far more components but are significantly cheaper.

I think it depends upon the application - for an EGT Gauge the Analog Device IC is the way to go.

For measuring inlet temps the price of the National Semiconductor ICs makes them more attractive but a bit more work (they may also be more sensitive to ambient temperatures - need to read up a bit more on them - the key is the ice point compensation).

Let me know about - the Knock Guage - having never seen one I was considering using a DSP - but that really is a pain.

From the looks of that circuit there is obviously a much simpler solution

Chris

john banks

£14.80 from Farnell

Chris.Palmer

LM35 £6 - LM335 £2.50 from www.maplin.co.uk

However I agree that the AD595 is a far superior device

[Edited to add]

These prices are of course just "noise" when you consider the price of a good K-Type Thermocouple & compensation cable.

[Edited by Chris.Palmer - 3/15/2002 5:56:36 PM]

john banks

And I thought I was a cheapskate

However, I do have a nasty habit of blowing these things up until I get the design right, so the cheaper the better

john banks

I think I have a neat little solution now Andy - I have been overcomplicating it a bit I think! Interesting when you try and work out a new project you find out about all sorts of components you had never discovered before

A low power low cost reed relay from RS should do the trick. There are some that need barely 10-12mA to switch and have an integral protective diode to save frying the LM3914 with back EMF when it turns off. Just a simple single pole single throw normally open one would do, which when energised connects your big automotive relay to ground.

On RS site : Automation:Relays&Solenoids:Reed Relays look for low power 12V NO with coil resistance of R=V/I where V=12, I is 15mA or less means we are looking for 800 ohms or higher if possible. Need to try and work out what current the LM3914N in the Knocklink is set for.

The SIL ones look the best:

291-9653
349-2890

Of course, if the voltage drop from 12V to the LM3914N outputs is low, then we could use the 5V models

[Edited by john banks - 3/15/2002 7:28:00 PM]

johnfelstead

Just a little pointer. You will lose power if you trigger the WI below 32 degrees Celcius air charge temperature. WRC WI systems switch on at 32 degrees and switch off at 28 degrees.

Nice thread.

john banks

Well in that case how about you do that AD595 circuit on your intake probe and feed it to a voltage comparator to keep the WI off under your set temperature?

But then what do you do if "Big Red" appears under 32 deg C? Or is it more chicken-egg - ie you knock BECAUSE you are over 32 deg C plus other unfavourable conditions, and really you should be tuning to avoid knock under 32 degrees even with WI off?

[Edited by john banks - 3/15/2002 8:11:06 PM]

Cosie Convert

John F makes a valid point, however I don't think charge temp is the ONLY factor dictating whether W/I is required.
For example if the engine internals, pistons, valves, manifolds etc are very hot from an extended thrash, if you come off the throttle for say 20 secs at high speed it is possible for the charge temp to drop relatively quickly due to rapid cooling of the alloy IC. Going back on WOT (on my car) requires W/I even although the charge temp is below set point.
I'm more concerned about the 25% power loss through a holed piston than 2% from an overcooled charge !!

Cosie Convert

Ideally my timing would be mapped to the charge temp as per GEMS
0.2 degrees retard per degree C above 40 deg C.

Even the later JECS, retarding on tracing knock and advancing almost instantly again would be a workable option. Although retarding timing on sensing knock IMHO is not the best option for max power output as it actually increases temperatures and to an extent is self defeating.

Worse than this, AFAIK, I'm stuck with an older version ecu which will retard and then remain retarded until reset My original ecu knocksensor has been disconnected so I now control knock by W/I

This probably causes less power loss that retarding the timing ??
Certainly keeps things cooler

john banks

The plot thickens. Disconnecting your Knock sensor is an interesting move - can see the logic on your car. I am trying to work out how the JECS determines advance so I know what I am doing when I adjust the MAF voltage. Will talk it through with you on Sunday if that is OK?

Cosie Convert

I think the best, perhaps only way to find out would be to have your adjustable MAF ratio unit as a handheld pot or similar, drive the car at a steady load and monitor the effect of an adjustment on the select monitor.
I'd also be really interested to find out what the MAP signal changes, IDC ? advance ? wastegate solenoid DC ? nothing ??

Do you think we can sweet-talk Dave B to bring the Select Monitor on Sunday

john banks

I won't have suitable controllers ready for Sunday, but checking what variables affect others with a Select Monitor seems the way forward.

[Edited by john banks - 3/16/2002 9:42:03 AM]

Cosie Convert

Checked my W/I relay tonight and it is 72 Ohms. Just to be sure to be sure, I checked the current and it was 200mA @ 14.4 volts Looks like that Ohms chap knew wot e wos on about

IIRC that means I can use option 1 or was it 2 or 3 or......