System monitor w/RoadRunner

nserpa9248 · 05-08-2008, 06:34 PM

I am looking at having a "System Monitor" screen in my RoadRunner application.
What i am looking to do is have this screen show:
-Vehicle +12v voltage
-Total amperage being drawn from system
-Amperage draw from each amp (2) and possibly the car-pc
-Temperature of each amplifier

The display would have each variable shown as a dial, with the number shown inside the dial under the needle (a lot like most motorcycle speedos)

What i am wondering is if the fusion brain can give me this kind of information that i can translate into roadrunner.

1-The vehicle voltage info seems to be obtained from a voltage divider. Is there optimal resistance for the two resistors that i would use for this?

2-I understand there is an amp-meter made for the fusion brain. However, i need one that will work with 4ga wiring (the one that is shown looks like it will accept appx. 12ga wire).

Does the fusionbrain amp meter shunt cause a voltage drop to my amplifiers. From what i have read, it is basically a very low value resistor. If so, how much of a drop will my amps get? My vehicle currently runs at 14.8 when running 12.5 when on battery.

3-Also, my two amps are fused for 50A (sub/amp) and 60A(4ch)..would the 50A amperage shunt be ok for that? (My amps have never blown a fuse btw)

4-As fas as temperature,i would get two of the temperature sensors (one for each amp) to show an individual read. Do those sensors have a D Shape to them? They seem to be cylindrical on the fusionbrain site..I would need a flat area to adhere it to the case of the amp with some thermal paste.

Does this sound achievable?
Hopefully i can get some better understand of the logistics of this whole thing so i can get the ball rolling on adding the fusion brain to the car-pc.

Thanks
-Nick

2k1Toaster · 05-09-2008, 10:55 AM

Quote: Originally Posted by nserpa9248

I am looking at having a "System Monitor" screen in my RoadRunner application.
What i am looking to do is have this screen show:
-Vehicle +12v voltage
-Total amperage being drawn from system
-Amperage draw from each amp (2) and possibly the car-pc
-Temperature of each amplifier

The display would have each variable shown as a dial, with the number shown inside the dial under the needle (a lot like most motorcycle speedos)

What i am wondering is if the fusion brain can give me this kind of information that i can translate into roadrunner.

The Fusion Control Centre main application such as version MDX can be embedded into RoadRunner no problem. So just like GPS, it will load the program in a little screen however you define in the configuration from graphics to functionality.

So yes it can.

Quote: Originally Posted by nserpa9248

1-The vehicle voltage info seems to be obtained from a voltage divider. Is there optimal resistance for the two resistors that i would use for this?

Quote: Originally Posted by nserpa9248

2-I understand there is an amp-meter made for the fusion brain. However, i need one that will work with 4ga wiring (the one that is shown looks like it will accept appx. 12ga wire).

I dont know of a direct-wire sensor that would accept 4awg wire. You would need to use a sensor that goes around the wire and measures the field it puts out. Meaning more expensive. As long as it has analogue output, you can use it with the Fusion Brain.

Quote: Originally Posted by nserpa9248

Does the fusionbrain amp meter shunt cause a voltage drop to my amplifiers. From what i have read, it is basically a very low value resistor. If so, how much of a drop will my amps get? My vehicle currently runs at 14.8 when running 12.5 when on battery.

Voltage drop is very very negligible.

Quote: Originally Posted by nserpa9248

3-Also, my two amps are fused for 50A (sub/amp) and 60A(4ch)..would the 50A amperage shunt be ok for that? (My amps have never blown a fuse btw)

For the 50A one it will work 100%. For the 60A one, it would be cutting it close if not overloading it. I do not suggest you use it with the 60A one without replacing the fuse to something closer to 50A and making sure it wont blow. Or place a 50A fuse in series before the current sensor going to the 60A amp. I very much doubt it draws 60A, except if you are blaring music at maximum volume. So for normal use you should be fine. But the 50A rating on our current sensor is there for a reason. Any more and it goes kablooey.

Quote: Originally Posted by nserpa9248

4-As fas as temperature,i would get two of the temperature sensors (one for each amp) to show an individual read. Do those sensors have a D Shape to them? They seem to be cylindrical on the fusionbrain site..I would need a flat area to adhere it to the case of the amp with some thermal paste.

Yes they do have a "D" shape to them.

Quote: Originally Posted by nserpa9248

Does this sound achievable?
Hopefully i can get some better understand of the logistics of this whole thing so i can get the ball rolling on adding the fusion brain to the car-pc.

Thanks
-Nick

Yup all doable.

And you have a good name.

-- Nick
Fusion Control Centre

Sonicxtacy02 · 05-09-2008, 11:15 AM

my rr plugin "rrfusion" will display sensor data in both raw and converted values as labels in RR. Check the RR plugins subforum for it and try it out.

nserpa9248 · 05-10-2008, 12:58 AM

i found a company who makes DC shunts rated for 150a (as well as a bunch of others). That says its made for 50mv output

http://www.deltecco.com/MKA-DC.html

they also offer some higher amperage models

http://www.deltecco.com/MKB-DC.html

would this kind of shunt work with the fusion brain?

Alanh · 05-10-2008, 01:59 AM

A couple of things come to mind using a current shunt.

First, if you have 50mV full scale into a 5V ADC for example, you need to look at the number of bits the ADC has to see if you've got the resolution you need. With a 50mV = 150A shunt, you've got 1/3mV per Amp so 1A = .0003333V, 2A = .0006666V, etc. So, used directly, most of the bits of your ADC reading will be zero. You might have to amplify the current shunt voltage to get more volts/amp.

I'm not a current shunt expert, but I've read that you don't really want to use one close to its rated capacity continuously because its basically a resistor and heats up. The number I recall is something like don't use it for more than 60% of the maximum rating on a continuous basis. I don't know enough about car audio amps to say the 50A shunt would have issues there.

Another consideration is where you put the shunt in the circuit. The ADC probably reads voltages referenced to its ground. If you put the shunt in the + wire, you have a voltage reading of 0-50mv except its 12V offset or so from ground. I don't think the Fusion Brain ADC will work with that. You could put the shunt in the ground lead, but now you've introduced a small voltage between the battery ground and whatever you're powering. Now that ground isn't really the same ground the rest of your system uses so you can get ground loops. If the negative power lead into the amps is grounded to the car chassis through any path (like your PC sound outputs), you've now got all kinds of issues including the fact that some of the amp current probably isn't going to flow through the shunt so the readings are off - maybe way off. There are circuits that allow you to use the chunt in the + lead, but it requires some electronic design and fabrication.

As already suggested some of the Hall-effect sensors that aren't directly connected to the wire carrying the current eliminate some of these problems. They have drawbacks too though: like cost, they need a power supply, and also a bit of circuitry to convert their output to a voltage. I've also heard that some inexpensive brands have some type of memory effect that affects their accuracy if you use them near their maximum ratings too.

nserpa9248 · 05-10-2008, 06:48 PM

After reading the info you guys have given me, i have gathered this (Let me know if im right)

The 50mv output from the shunt may be too low for the fusion brain to pick up, or notice the .000xxv changes. Can a hardware developer of the FB let me know if it is sensitive enough.

They also offer a 100mv versions too..i imagine that one would give me a more accurate read.

With your math of 50mv 150A shunt saying that for each Amp i am getting 1/3 mV. So, would that mean with a 100mv 150A shunt i would get 2/3mV for each Amp?
...figuring you are going by amperage rating divided by milliamp rating
Translating into 1A = 0.0006666V / 2A = 0.0013332/ 10A = 0.0066666

I agree with what was said about the shunt rating...I have also read about only using a shunt to 2/3 its rated power. The site i listed above states that as well.
My sub amp is rated for 50A (fuse rating...it never draws that much)
My 4ch amp is rated for 60A (fuse rating...it never draws that much)
I am aiming to get atleast a 100A rated shunt.

Next, as far as placement i would be placing it on the +12v power wire right before each amplifier, after my distro block.

As far as the voltage..could i use a voltage divider (as discussed earlier about getting vehicle voltage) to get the cars ~12v down to what the fusionbrain will understand? (0-5v)
Or would that mess with the reading from the shunt?

I think the hall-effect way will be too expensive, to bulky, and too time consuming to set up right....i would really rather use an analoge shunt.

Thanks for all the help guys,
-Nick

greenman100 · 05-11-2008, 10:07 PM

You really need a shunt and an op-amp to isolate and scale the voltage.

nserpa9248 · 05-12-2008, 12:00 AM

thanks greenman...did some reading on operational amplifiers.
Drew up this diagram below to show what i belive is how an OP-AMP would be used in my scenario.
Sorry for all the confusion on this guys, new to alot of this.
I appreciate all the help :-D

V+ and V- would be directly connected to the shunts 50 or 100mv output.
Vs+ to the positive side of the power supply
Vs- to the negative side of the power supply
Ground to ground
and Vout to one of the analog inputs into the fusion brain.

As far as obtaining an OP-AMP radioshack shows they sell two models
a TL082/TL082CP Wide Dual JFET Input Op Amp (8-Pin DIP)
http://www.radioshack.com/product/in...rt&tab=summary

and a LM741CN Operational Amplifier (8-Pin Dip)
http://www.radioshack.com/product/in...entPage=search

would either of these work for the application i am using them in? I am not sure how to get one that will work on either regulated or unregulated 12v (for the power supply) and how to figure if it gives me the right ouput (0-5v) for the fusion brain.

greenman100 · 05-12-2008, 04:58 PM

close. You're getting there. I'm impressed you;re reading up on op amps.

You need some resistors with the op amp to set the gain. go read the wiki on it

nserpa9248 · 05-12-2008, 09:07 PM

I did...and i think it is way over my head of electrical engineering lol. Im self taught with alot of this stuff.

Let me take another look at the wiki..i think i can decipher it...

greenman100 · 05-12-2008, 09:08 PM

Quote: Originally Posted by nserpa9248

Im self taught with alot of this stuff.

Me too.

If you have specific questions, I'm happy to answer them... it's just impossible to teach 4 years of electrical engineering to everyone.

nserpa9248 · 05-12-2008, 11:52 PM

Update on my "research"

I have been going over the wiki and alot of other stuff ive searched from google on these things (op-amps)

I seem to have two options
either i need a differential amplifier, so that i can take the two positive outputs from the shunt (one being the "un-altered" voltage and the other being 0-50(or 100)mV less) and get an output voltage from the op-amp which is a function of the difference of the two different voltages...which...hopefully i can get to be 0-5v (doesnt look like this is possible) if i can not do this, i would need to add another op-amp after the differential amp in series into the FB input
Shown below

Or

Use two separate op-amps one having the input voltage being the "un-altered voltage" from the shunt, the other op-amp having the input voltage as the "altered voltage" and having the fusion brain see the two voltages from the op-amps outputs and doing the math via software.
I am not quite sure if i would need to use inverting or non-inverting OP-AMPs (trying to do the math with the resistance values to see which will suit my needs)
so i drew a diagram for both

Dual Non-Inverting Op-Amps

Dual Inverting Op-Amps

Using the second option would obviously take up four of the analogue inputs into the FB, which is fine, i only need two more for the temp sensors, and one for the voltage sensor

so 7 ports will be used, three left for future sensors

greenman100 · 05-13-2008, 06:36 PM

your first option is exactly what you want, just make sure the FB and the op amp share the same ground.

nice work btw.

nserpa9248 · 05-14-2008, 04:12 PM

thanks.

I did the math on the differential op-amp, and found a resistor combo that should work great for me.

Here is the calculation

I am figuring the V1 input being the "un-altered" voltage (distro side of shunt) and V2 being the "dropped voltage".

I figured these resistor values would work:
R1-9,500 ohms
R2-10,000 ohms
Rf-3,800 ohms
Rg-10,000 ohms

With those calculations, if i did my calcuations correctly this table is correct.
The concern that i am having is the very slight voltage changes when the amperage changes.

For example:
When the voltage is 8V and the current draw is say 50% (50mV drop) the output voltage is 7.995V. When the voltage is 8v and the draw is 0% (0mV drop) the output is 8v. This is only a .005V drop between these two situations.

I am concerned about if the fusion brain will be able to read that little of a difference.

Are my calculations correct?
Will the fusion brain be able to read these small differences?

nserpa9248 · 05-14-2008, 05:29 PM

i did some searching on fusion brain accuracy

I came up with a thread on the temperature sensors.
Greenman, this post you made
http://www.mp3car.com/vbulletin/1178983-post5.html

Quote: Originally Posted by greenman100

Displayed are the raw voltages. Converted, they are as follows:

Code:

Raw Volts	deg F

0.879765	76.286
0.869990        75.38369231
0.879765	76.286
0.889541	77.1884
0.889541	77.1884
0.874878	75.83489231
0.874878	75.83489231
0.899316	78.09070769
0.889541	77.1884
0.889541	77.1884

Shows that one (of many)of the raw voltage values you were able to read was 0.879765 volts
which is an idication the fb can read up to the millionth place, it seems that i would need accuracy up to that point.

Can somone verify this as well as the previous question on my calculations.