# Thread: 4 Channel Input Isolator and Voltage Divider

1. ## 4 Channel Input Isolator and Voltage Divider

I've purchaed several of these boards. What I haven't been able to find on this forum or Fusion site is where to position the jumper on the 3 pins to get 15 volts vs 7 volts. Can anyone help. I don't want to ruin my board.

2. Nick designed these. I'll get him to post instructions. In the meantime, don't hook it up just yet.

3. http://www.mp3car.com/vbulletin/fb-s...e-divider.html

Answered in there now posts #2 and #3

4. ## Issue with the isolator board.

I'm using the isolator boards between 12v battery banks and the fusion brain. Setting up the isolator boards for 0-15 volts, I tested using a 9v battery, with no input to the fusion brain.

When I inquired, Nick let me know that: "The 15v input should only work between 10v and 16v. I have attached an old output graph of the beta versions of the isolator boards. It has since been smoothed out, but generally the ranges are the same for these production boards."

I have attached the output graph to this post (I hope). Using the 0-5 volt formula in my application, when I apply 12.5v to the input, I get a reading of 0.2 volt. Looking at the graph, one would expect a value of around 2.5 volts.

Any ideas as to what the problem is?

What would be the correct formula to use in applications?

5. Well, I figured it out. Had the formula messed up.

6. I am going to be characterizing the production boards and get an exact forumla for them in the next few days. I have to get a variable power supply, since now that i am graduated I cant use the fancy toys in the university

7. ## Power Spike Question

I'm using 110vac to 5vdc transformers(the simple plug in the wall type) to sense the existance of power on my boats two shore power inputs. At the dock it is not uncommon for the power to go down. When the shore power comes back up, I feel certain that there is a spike. Do I need to use the isolation board between the 5v transformers and the fusion brain analog inputs?

I also use the same type transformer to sense power on the inverter circuts, but I don't think that is an issue, because the inverter doesn't come off battery power untill the shore power is stable. What do you think?

That brings up another question, when measuring battery voltages, particularly on the high amp inverter batteriy bank, should the sensor cable be fused, if so what amp fuse should I use, and does it matter where the fuse is physically located(ie at the battery bank, near the board, etc)?

Thanks

8. Originally Posted by jctman
I'm using 110vac to 5vdc transformers(the simple plug in the wall type) to sense the existance of power on my boats two shore power inputs. At the dock it is not uncommon for the power to go down. When the shore power comes back up, I feel certain that there is a spike. Do I need to use the isolation board between the 5v transformers and the fusion brain analog inputs?
Simple transformers generally toss out what you put in. Put in a spike, and you get a spike out. Now that spike might not be very big once it goes through the windings, but it should still be there. If it is more than about 5.2v, thes you definately need protection of some sort. But I am guessing the dock has 110v and your boat has a battery bank correct? If you are powering the FB from the battery bank, there should be a controller/regulator on the output already, so it should be fine. The voltage isolators will work and this is something they excel at. Only problem is if using with various types of sensors, you will need to add scaling resistors to everyone to make the range in the correct area for the sensor.

Originally Posted by jctman
I also use the same type transformer to sense power on the inverter circuts, but I don't think that is an issue, because the inverter doesn't come off battery power untill the shore power is stable. What do you think?
The batteries should act as giant capacitors and essentially smooth it out a bit. Then when it is sent through the output controller (which I assume you have to get usable voltage out), it should account for input/output differences, but who knows what your model does.

Originally Posted by jctman
That brings up another question, when measuring battery voltages, particularly on the high amp inverter batteriy bank, should the sensor cable be fused, if so what amp fuse should I use, and does it matter where the fuse is physically located(ie at the battery bank, near the board, etc)?

Thanks
The sensor cable will be drawing less than a couple hundred milliamps and depending on the input voltage, just a few milliamps. The most important thing is that the cables dont short. If you are worried about it, then you can add fuses. It doesn't hurt but it is generally not needed. But if for some reason it melts and starts a direct short, that fuse might save your boat.

9. ## voltage divider jumper settings

I went to to posts 2 and 3 referenced on the other thread but it doesn't make sense!

When holding the board where the text can be read, my pins are not up and down, they are sideways!

So, is the 15 volt setting the right or the left set of pins. Why can't you put it on the beautiful pictures of the board in the thread?

I like the product but the documentation is lacking...

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