Powering sbRIO with a DC/DC converter.

[akeister]

I have an application in which I'm powering the sbRIO 9642XT unit off a DC battery. Rather than have to invert the battery's DC into AC and then back into DC again, thus losing efficiency, I'd like to power the sbRIO directly off the battery bus. The problem is, the battery bus is at 48 volts, not the required 24 volts for powering the sbRIO. In addition, the sbRIO User's Guide says that the power supplied to the sbRIO needs to have a peak-to-peak ripple of less than 20 mV. I'm having a hard time finding a DC/DC converter that will fit the bill. 

To summarize: I need a DC/DC converter with input at 48V, output at 24V, capable of putting out the 8 W necessary for an sbRIO (I'm not using any 5V TTL lines, or expansion modules), and having less than 20 mV peak-to-peak ripple. Does anyone know of a such a converter?

Thanks!

[esmaham]

Hi Adrian,

I will look around and see if we have any suggestion for you. As far as I know, we don't have such a converter at National Instruments.

Thanks and have a great day.

[Spex]

Hi Adrian,

Finding a power supply or DC/DC converter with less than 20mVpp ripple is pretty challenging and expensive.  The 20mVpp spec is pretty conservative in order to meet the accuracy specifications of the analog input circuitry (because they don't have an isolated internal power supply).  If you are not as concerned with the accuracy of the analog circuitry, you can choose a DC/DC converter that falls outside the 20mVpp ripple range.  The device will still power correctly and all systems will operate.  If you are concerned with the analog input accuracy, you can improve the output ripple voltage of a DC/DC using an external power supply filter. 

For projects within NI, we've used the 9-18VDC version of this DC/DC (Model JCL3012D12) from XP power to run Single-Board RIO from a 12V battery.  XP Power also sells a 48VDC Nominal DC/DC.

http://www.xppower.com/orderPriceList2.php?seriesid=100504&lang=EN

The DC/DC is just a component (through-hole design) so we've had to whip up either a breadboard design or a simple PCB with screw terminal inputs and outputs for our projects.

Regards,

[akeister]

Thanks very much for the info, especially the bit about the trade-offs between ripple and analog accuracy. Since we will be using analog inputs, but we're not hyper-concerned with accuracy (we don't even do system calibrations here!), it sounds like the converter you mentioned would work fine, although we might want to find a DIN-rail-mountable one that is equivalent. Thanks again!

[akeister · Accepted solution]

And the winner is...

The TRACOPOWER TCL 060-124DC. It has the correct inputs and outputs, and has less than 50mV ripple, pk-pk. It also puts out a decent power, so I can power all my sbRIO's from the one converter. Finally, it's DIN rail mounted, which was especially nice for our situation. 

You can get this converter from Newark - it's Newark part # 51R4740. 

Cheers.

[freemason]

Hi Spex

needed small info,

in your reply you mentioned that you used Model JCL3012D12, but its output is only 12 V and the SBRIO takes 19-30V , can you please tell me how are your able to power it up with 12 V ? are you using 2 different devices in series to get 24 V?

For projects within NI, we've used the 9-18VDC version of this DC/DC (Model JCL3012D12) from XP power to run Single-Board RIO from a 12V battery.  XP Power also sells a 48VDC Nominal DC/DC.

http://www.xppower.com/orderPriceList2.php?seriesid=100504&lang=EN

The DC/DC is just a component (through-hole design) so we've had to whip up either a breadboard design or a simple PCB with screw terminal inputs and outputs for our projects.

Thanks

[Spex]

Hi freemason,

I apologize, but I missed your response question in 2011 and was it was just brought to my attention in the form of a private message asking the same question. 

The part I mentioned is the part we've used.  In the datasheet, you'll notice that the JCL3012D12 part is a dual output part at +/- 12 V.  If you power the Single-Board RIO from the combination of the +/- 12V rails, you have a 24V supply.  I'm including a schematic (provided as-is 🙂 )from a PCB we put together to be absolutely clear.

Hope this helps anyone else who comes across this thread.

Cheers,

[Nathan_B.]

I am trying to figure out this powering thing for my sbRIO-9632.  You say that the ripple can adversly affect the analog input accuracy.  To what extent does this ripple affect these values?  I plan on reading from a load cell/strain guage bridge which will have relatively small ouput voltages.

The XP power converter that you use shows that it  has a 70mVpp ripple and I found one that has a 40mVpp ripple.

The other issue that was brought up to me by a friend is that if I use a ±12V supply then the ground of my motor controllers will be 12V different from the ground of the sbRIO.  I'm told that when I send the PWM, I would need to shift my signal by this 12V difference.  Is this correct?  Should I be concerned here?

[Dave.C]

Hi Nathan,

What is your expected voltage range?  It's difficult to say how much the ripple will effect the accuracy as the specifications are based on a ripple of less than 20mVpp.    

What motor controller are you using?

[Nathan_B.]

We will be using Lipo batteries with Mamba Max Pro ESCs (designed for RC cars). The nominal voltage on the Lipo batteries is 22.2V but they charge upto ~25V.  I realize that this is in the range of input voltages but I would like to have something to 'separate' it from the high current devices (as well as limit the board's current draw since it has a non-replacable fuse).  The DC DC converter that I found looks promising but if I'm unable to get some of those, I want be able to use the ±12V ones by XP Power and hence the concerne with the grounds.

However, on Saturday, I happened to have a DMM out and decided to measure some voltages on the Starter Kit (DaNI).  I measured from battery ground to the sbRIO ground (-12V) and it shows ~0V so that just made me even more confused.

The concern regarding the accuracy of the AI's is that we want to read the output of a load cell (strain gauge bridge) which, as you may know, has very small output voltages.

(Note:  I'm not super experienced with all of these electronics, I'm the LabVIEW/RIO advocate to our team)