Question on using JimStim for MS3 testing...

[hobieboy]

I'd like to test the sequential Injectors and Ignition outputs on MS3. These are accessible only from the J1 / J2 headers on the MS3 daughter boards.

So, would it be ok if I connect these outputs to the 10-pin header on JimStim that drives the 6 LEDs?

One other un-related question: how do I simulate different MAP inputs? I have a compressor but what's a safe way to apply pressure to the sensor to simulate different MAP conditions?

[racingmini_mtl]

Neither the JimStim nor the J1/J2 header are designed for this purpose. Having said that, it should work but in an inverted way (LED on when the output is off) and the MS3 CPU pins should be ok to drain the 15mA from the LED circuits.

There is a plan to offer an addition to the JimStim to test the MS3X I/Os but this would still not be designed to connect directly to J1/J2.

In any case, you will need something to connect between J1/J2 and the outside world so you would be better off testing with that interface. And if you're waiting for MS3X, then you should also wait until you have it to test these outputs.

If you can't wait then the best would be to use a 1K resistor and a small NPN transistor (2N3904 or PN2222) and connect the resistor to the J1/J2, the base to the other side of the resistor, the emitter to ground and the collector to the JimStim LED. This will emulate the injector or ignition driver circuit and give the correct results in a safe way.

As for testing the MAP input, you can use a syringe and a small length of tubing. This allows you to create pressure below and above ambient. Or simply suck or blow on the tube (seriously). Of course, neither method will give you a calibrated pressure but you can easily check transients and low and high pressure conditions.

Jean

[hobieboy]

Thanks for the explanation Jean. Indeed much safer and realistic to drive the LEDs at the transistor output side.

One question: using a small transistor like 2N2222 vs a TTL buffer - is there any functional difference?

[racingmini_mtl]

Thanks for the explanation Jean. Indeed much safer and realistic to drive the LEDs at the transistor output side.

One question: using a small transistor like 2N2222 vs a TTL buffer - is there any functional difference?

The transistor circuit is designed to drain the current from the LEDs like an injector driver or an IGBT would do. The TTL buffer is designed to source current (or voltage) to a device. Also, the transistor inverts the signal but the TTL buffer can invert or not depending on the buffer used.

And the JimStim ignition LED circuits are designed to be connected to a grounding circuit. If you want to test a TTL buffer output, you'd be better off using the IAC leds with one side connected to the buffer and the other side connected to ground.

Jean

[hobieboy]

The transistor circuit is designed to drain the current from the LEDs like an injector driver or an IGBT would do. The TTL buffer is designed to source current (or voltage) to a device. Also, the transistor inverts the signal but the TTL buffer can invert or not depending on the buffer used.

And the JimStim ignition LED circuits are designed to be connected to a grounding circuit. If you want to test a TTL buffer output, you'd be better off using the IAC leds with one side connected to the buffer and the other side connected to ground.

Jean

My plan is to have the Inj outputs from J2 drive your P&H board so I guess I can't have it both ways easy If I use a 2N2222 then I'll need to add the +5V pull up before hooking it up to the P&H, but need to disconnect the pull up before testing it with JimStim LEDs. Hope I get this part right?

[racingmini_mtl]

Actually, you don't want to 2N2222 to drive the p&h board (assuming you meant the V1.1b) because that would invert the signal. So you'd use it only for testing on the JimStim. You want to connect the p&h board directly to the J1 header (like you would for MS3X).

So the best would be to install the p&h board and test its outputs on the JimStim LEDs. That's how I'm setup for my bench testing.

Jean