PNP Harness missing component
 

Hey everyone,

I just bought a used Adaptronic e420c to retrofit into my '99 NB. In preparation I've spent the last few weeks reading through what seems like every thread in this subforum trying to familiarize myself with this system.

Well, the package arrived last night containing the ECU, an '01+ PNP harness and a partial '99-00 PNP harness. I plan on soldering the Adaptronic plugs onto this latter circuit board.

In looking through the wiring diagrams and pinouts and comparing them to the circuit board, I noticed that there is a small component missing from the board labeled BAT54S.

Here's a picture:
https://www.miataturbo.net/attachmen...ine=1358952669

My questions are: what was here? Is it needed? Where can I find one to replace the missing piece?

Thanks in advance for any and all advice!
Aiden

I believe that pin is 2D which connects to the VSS.

Just found a missing 1K resistor as well:

https://www.miataturbo.net/attachmen...ine=1358954044

Again: Purposefully removed? Broken off and missing?

lol. I hope the PO added those and not the maker of the harness...

those look to be pull ups. I'm assuming the two are for the crank and cam sensor inputs.

So take a moment to school me if you would and just assume (everyone else does) that I'm a complete idiot. A pull-up resistor is used to modify current (and therefore voltage) to get an input voltage to a specified level (5V, 12V, etc.)? Does it act as a sort of a modulator to protect from overcurrent?

very lame-man's verison:

when the sensor "outputs" the signal it's really just switching the wire to ground momentarily. Without a pull up, there's no reference for the ECU to know when the signal is inputting.

So the pull-up provides a constant 12v signal the the ECU "reads", then when the sensor triggers, the voltage drops and flows to ground instead of into the ECU, and the ECU can register the voltage drop to ground and thus register a sensor event.

Without the pull-up, there would be no change from high to low voltage, it would just be a wire going from, more or less, nothing to nothing and the ECU cant do anything with that.

Thanks again Brain for helping me to get that straight in my head. To be clear that I've got it: the ecu is reading the difference in voltage between the 12V (or 5V, etc.) pull-up is supplying and the sensor's grounding effect.

Is this a voltage differential or is the sensor grounding several times in lightning fast succession (a time event)? In other words, does the sensor restrict the amount of voltage going to ground (like a potentiometer of sorts) based on the conditions being monitored?

One more question: why use resistors as pullups? Is this to keep a very even (and therefore measurable) voltage out to the sensor?

And back to my original question: does anyone with Adaptronic knowledge know if the transistor shown in the first post is necessary in a 1999 NB application? If so, where do I find one to solder in?

Thanks again in advance!

to limit the amount of current. it just needs a little voltage, it doesnt need to povide power to run something... otherwise it would cause faults and blow up.

Correct.



There are two different applications where pullup resistors are used.

In the case of a "digital" sensor, such as a crank or cam sensor, the sensor is "grounding several times in lightning fast succession" as you put it. It needs to indicate to the ECU the precise moment when, say, a tooth on the crankwheel passes the sensor. In that case, the output switches when the tooth passes in front of the sensor, and then switches back when the tooth leaves the sensor's field of view.

For analog signals, like temperature and pressure, the sensor itself is a variable resistor whose value changes along with the temperature or pressure to which it is exposed. In this case, the sensor, in series with the pullup resistor, forms what's known as a voltage divider. The ECU measures the voltage at a point between the pullup (which is a known, fixed resistor) and the sensor (which is a variable resistor), and can deduce from that voltage what the sensor's resistance must be, and therefore, the pressure or temperature which the sensor is measuring. In the link above, the pullup is R1, and the sensor is R2. Vout is where the ECU measures the signal.


In the case of digital circuits, the resistor is there simply to limit the amount of current flowing through the circuit. If you connected directly to 5v without a resistor, and then grounded that, you would have created a short circuit. That would mean destroyed components, blown fuses, etc.

For analog circuits, the resistor forms one-half of a calibrated circuit as I've described above. For this reason, it's important that pullup resistors in analog circuits always be of a specific value, whereas in digital circuits it doesn't really matter so much.



I can't tell you what it's for, but BAT54S is a pretty common Schottky diode. Here: BAT54S,215 NXP Semiconductors | 568-1614-1-ND | DigiKey

Joe says things more "spreading the geek" than me. But it looks liek we are saying the same things :)

Scott sometimes sneaks in with a quick answer while I'm composing long diatribes.


Spread the geek, bro. :D

honestly, everything i said is something you probably already posted once, and i just reposted in a way i can comprehend with as little "big words" as possible.

And to think I came to post on mt.net only after meticulously crafting a flame-retardant suit... Thanks to both of you for schooling me on pull-ups. The last electronics class I had was in 1986 :eek3: in 10th grade. Of course we were still programming Apple 2e's in BASIC as well...

Thanks Joe for the link to where I can purchase the transistor. For the shipping cost, I may try a local vendor first. Does Radio Shack still carry anything but cell phones and gps units??? Guess we'll find out soon...

Go kill yourself, newb.

:D

I honestly don't know why we have that reputation. Well, I take that back. I know exactly why, but it's not relevant to folks who care enough to craft coherent sentences, express ideas in a lucid and meaningful way, and generally come across as reasonable human beings, rather than six year olds who just learned how to use profanity.


I can absolutely 100% guarantee you the Radio Shack does not carry this part or anything like it. It's not a transistor, it's a diode array (two diodes in one package), and they're schottkys.

If there are any electronic shops around you which stock NTE, the equivalent part would be NTE637. There's a chance that Fry's might have it. They don't list it on the website, but you never know.

Or you could just order it from Digikey. (I can't count the number of orders I've placed with there in which the shipping was more than the part. Hint: use USPS.)