Where do you get 5 volt supply voltage for extra AN inputs?

Does the datalogit have a supply to tap from, I haven't been able to find one.

If not were do you get a clean supply of 5 VDC +-.25.

Any suggestions?

 

The 0-5V DC comes from the signal output of the sensor you are trying to log. Most sensors on the market are 0-5 volt. SOme however are 0-10 v and require a 50% voltage divider before hooking up to the datalogit.

 

The sensor I am using is 0-5v, I just need a stable feed so it doesn’t fluctuate while logging/driving.

What do you think about this? I was recommended to use the voltage going to the MAP sensor. How much can you pull out of this line with out effecting the map sensor?

I would prefer not to mess with critical systems, as I admittedly do not fully understand the consequences for my actions with electricity, so I prefer to be a cautious cat.

Jeff: Also wondering if it would be possible for us carputer guys to just tag into the 5VDC from the power supply? Have you thought about that, and is it a stable source of voltage?

Currently I am using the voltage coming out of my LM1 (O2 feed back line 1 reprogrammed to supply 5VDC over the entire range of afrs). Though using this method, I get a lot of lag while the WB meter is warming up initially at startup.

I plan on running an entire gamut of aux sensors, so I am wondering whether or not I should find a separate supply that is regulated well or if it will even be necessary.

Does everyone else just find a sufficient existing 5 volt supply and just run with it? Are there any good methods of isolating each sensor so the corrections (AN1-AN2 or AN3-AN4) are not necessary?

Thanks for the help.

 

My Question to you

#1. does the sensor you are using require a 5V+ INPUT?

Most aftermarket sensors use a 12v+ input, ground to the block and the sensor internally generates a 0-5v+ OUTPUT.


Your Questions


#1. Is it possible for us carputer guys to just tag into the 5VDC from the power supply?

Yes, if you need a regulated 5V an OPUS (or its equivalent) does allow that or alternately I can send you the schematic to make a regulated 5 Volt PS for under $20 and about 20 minutes with a soldering iron.

#2. Are there any good methods of isolating each sensor so the corrections (AN1-AN2 or AN3-AN4) are not necessary?

Nope, as long as you are using the FD ground system you will get the fluctuations in DC volts on the GRND line.

#3 I was recommended to use the voltage going to the MAP sensor. How much can you pull out of this line with out effecting the map sensor?

The map sensor 5V in is a regulated 5V coming off the Power FC box at pinout 3I. It runs a ton of stuff and is probably beefy enough to handle one or two more low drain accessories.

 

I believe it requires as 5V in from what I understand, I would link the full spec sheet but it is to big in PDF and the link is dead from the thread involving this sensor. It requires 5mV peak I believe, how this would factor into the equation I am not sure but I am taking it that this is a relatively small amount and should not tax almost any system I would feed from. I am just reluctant to plug into the MAP as it seems like a pretty important system, and I can probably find a better source.

Thread about sensor
http://www.innovatemotorsports.com/f...read.php?t=151



I am using it for fuel pressure and oil pressure and it is the 0-100 Psi variant of the sensor.

 

For the 5 volt circuit you mentioned is it similar to this one? Would this be the best route if I already have other forms of 5 volt power?



I am not very clear as to what will cause the fluctuation in the grounding system, and can this be avoided or resolved?

Is there a way to isolate the system completely, or is this really a issue I should be worried about?

I see what seems to be a large amount of fluctuation in the readings from the sensors at idle and at constant load, so I am assuming that this is due to the power source and would like to test to find out if I can stabilize the sensors at all if any.

Would powering the sensors off a separate battery source be the way to test for tolerances in the existing system.

 

Yup, you are right it does require a 5V DC input. It however seems to have a peak draw of 1.0 mA which is pretty damn small. However, if you are more comfortable the outboard system is a good way cheap was to go----see my answer to your next post about the schematic.

 

Yup that schematic is as good as any for a five volt regulated PS. The regulation is done by the 78xx regulator. It will probably be good for about 1 - 1.5 A (1000-1500 mA) output if you use a good heatsink with the regulator. You can see why, in my previous post the 1.0 mA draw from the sensor doesn't bother me/

The fluctuations in the grounds are as a result of the FD system and are inherent to the FD....you can't fix them because the FD ecu uses the ground system to carry data and control subsystems. Check out "floating ground issues" on the forum.

The problem with running the sensors off their own battery is that the datalogit is still going to be seeing the ground from the FD. I suppose the AN systems can be made separate by using the negative lead from the external battery but you will still limited to 2 inputs since you will have to run the battery negative to the AN2 and AN4 positions and compute the delta functions.

 

Here's a different 5 volt supply with a couple of safety features (zener and resistor). Thanks to the guys at Autospeed for the design. Using a stout heatsink, I have powered a USB hub and Sound Blaster Audigy external soundcard with this baby.

 

Thank you very much for your time and help Jeff!
I will read up on that topic when I get a little time.

Is the "floating ground issues" a oversight in the datalogit system or just a mandatory problem to deal with inherent in tacking on to the existing Mazda system?

And I was wondering if you could quantify the errors involved with the floating ground issue, if you can even do that. How much of a variance have you observed?

I can pressurized my fuel system and can see the mechanical gauge on the FPR alongside the readout on the “watch” screen, the output will fluctuate over a fairly high range ~5 Psi. It will bounce back and forth between a high and a low rarely seeing intermediate values. The fuel system holds pressure at around 40Psi and drops slowly ~20-30 min to 0, so the actual pressure is fairly constant compared to the AN outputs fluctuating readings.

This does sound excessive doesn’t it for the tolerances the sensor should have wouldn’t you think?

 

The floating ground issue is FD specific. OEM, PowerFC whatever ECU the ground fluctuates. I really have no data why the ground floats or even if it is quantifiable as a constant, but I suspect that there is no real way to predict what the ground value is going to be at any time.

As to the differences you see in the other sensors, I can only analogize it to the problems that Chuck W. talks about when attempting to correct MAP sensor readings. Have you tried to use the delta function on the datalogit with the FP sensor? If not go to A. If so, go to B.

A. Try putting your 0-5 volt FP sensor oputput at AN1, take any ground and put it to AN2. Go to setup AUX. and click the Delta AN1-AN2 box. That should stabilize the differences in the + and - due to floating ground problems.

B. Your fluctuating readings may have something to do with the sample rate (lines per second) of the datalogit. How many lines per second are you logging? The more lines per second logged, the more stable the data appears. You can increase the number of lines per second by decreasing the number of parameters monitored.

 

Another source that I am considering is the plug on the side of the PFC. It is a barometric readout for the PFC that utilizes the stock map sensor when using the apexi 3bar sensor.

This source has a 5 volt output, but I am wondering how many mA can be pulled from the circuit?

I need to run 3 extra sensors that each pull 5mA, will this be OK to tap into the source?

What does the stock map sensor require under load?
What can the PFC supply out of this port?

Can I run the stock map and the 3 aditional sensors for datalogging with a additional load of 15 mA peak from the same source?

 

I really shouldn’t have tried it till someone chimed in, but I wanted to finish my wiring wile I had time, and Jeff sounded fairly confident that it should hold.

As far as I can tell it is fine to run the stock map and a additional 15 mA off from the side barometric port. Sensors seem to be operating fine and no odd fluctuation from what I have logged or noticed.

Does anyone have any info on whether or not this will work over a extended amount of time, or be harmful if left? Will it burn out a driver or something if load increases for any reason?