BNB Products DPR-100

Introduction

My thanks to Bret of BNB Products for the supply of the DPR-100 for review.

The DPR-100 is an onboard digital power recorder. The device monitors several different important electrical power statistics of a model whilst in flight. The device records this data onto its onboard memory chip and the data can be later downloaded to a PC for analysis. Additionally the latest version can also run in 'live mode' and deliver data to a PC in real time. The device being reviewed is suitable for up to a 30 volt input and up to a 100 amp current load. Although it does support a "High Voltage" configuration allowing up to 60 Volts if two equal battery packs are being used in a series by connecting only one pack through the DPR.

The device itself is very similar in size and weight to an electric speed control such as the Castle Creations Phoenix 35. The actual size being 1.6 inches x 1.2 inches and the weight being 25 g or 0.9 ounces.

Before I cover some more of the technical specification here are some pictures of the device itself :

 

Overview

As previously mentioned this device can record to an internal chip and later the data can be downloaded to a PC for analysis. Each time the device is powered on it creates what is referred to as mission data. Mission data is just the data recorded by the device between power on and power off. Several missions can be recorded and then downloaded later for analysis.

Depending on the settings of the device it is possible to get over nine hours of mission data before having to reset and erase the data on the device. Additionally (again depending on settings) the device can record between one and fifty samples per second per channel. The power analyzer has three primary channels for recording voltage, current and power. The secondary channels can be connected to optional temperature monitors to record temperature from two temperature probes or alternatively RPM using a hall effect sensor and magnet. The RPM sensor can also work by detecting magnets within a motor and sensing RPM directly from the motor itself.

One of the two available temperature monitors is just a straight forward temperature probe (two probes), the other is a temperature probe and LED. The temperature probe has dual temperature probes which allows for monitoring of both the lithium pack temperature and the motor temperature during a flight (as would be typical when using this device with a Swift). Obviously monitoring an out runner temperature can be a bit problematical due to the motor can spinning but in runners are easily monitored.

The RPM monitor consists of a hall effect sensor which plugs into the same pins on the DPR-100 as the temperature monitor, so you can either monitor temperature or RPM but not both. The sensor comes with four small magnets. More on this later.

All of the items come with explanatory information in the form of booklets which are more than adequate in describing the functionality of the various devices. Included with the digital power recorded itself is a connection lead for connecting the device to your computer and a CD with the drivers and graphing software for plotting the mission data.

The digital power recorder requires some connectors for its four input/output leads. I fitted four millimetre bullet connectors as these are what I use on my lithium packs and speed controls. The instructions make it very clear that the digital power recorder does not have a designated input or output set of connection leads, it will work out for itself what is the power source and what is the load to be measured. This is very useful as it makes connecting the digital power recorder very simple, quick and easy with no need for fumbling around trying to work out which wire is input and which is output.

The device comes factory set to begin recording two seconds after it has been connected to a power source. This is configurable within the supplied software. Also configurable within the software are the data sampling rate, data recording resolution, recording trigger and channels to record. Changing the sampling rate directly affects how long the device can record data as does increasing the number of channels that the device is recording from.

Software

The device connects to the PC through a supplied USB cable after which the mission data can be downloaded from the device and it's internal memory cleared. Some pictures of the software interface are below :

 

DPR-Graph Main Display

Live Meter Display

 

One of the new functions on the DPR-100 is "live meter" and 'live graph". These two modes allow the DPR-100 to be used in a bench test type environment connected to a PC via the serial/usb interface. The DPR-100 then relays the live data from the model to the software on the PC screen where it can be monitored. In this mode data is not recorded just displayed real time. Either a real time graph can be created or alternatively the data can be displayed via the Live Meter Display where current, max and min values are displayed in real time (as can be seen in the picture above).

The graphing parameters of the program can be configured to display mission data in a variety of different ways to allow easy reading. The graphing parameters window is less interesting than the recording parameters window. The recording parameters window is where you configure the DPR-100 and define exactly how it will record it's data for any one mission. The samples per second slider determines how often the device will take a reading from its various inputs. As you change its value the max recording time changes. A high sample rate reduces the maximum recording time significantly. The sample channels check boxes allow selection of what inputs to monitor, again the more check boxes that are checked the more the max recording time reduces. The maximum record time is 9 hours with a very low sample rate. At the other extreme, recording at the highest sample rate and across all four channels will give 3.58 minutes of mission recording time.

The recording trigger defines how the device will initialise. By default this is set to a two second delay, meaning that recording of mission data will occur two seconds after connecting the battery to the device. The trigger can also be set to begin recording when a specific Current load is reached.

Temperature & Tachometer

The settings on the right-hand side of the recording parameters window are all to define what happens when using the optional temperature LED. The settings are all thresholds that when crossed result in the TMP-LED's LED flashing.

One new addition is the tach (pulses per final drive). This parameter determines how many magnetic pulses there are per revolution of what you are monitoring. So if you have mounted one magnet in your heli's main gear then this should be set to 1. If you are monitoring your motor and it has six magnets per revolution then this value should be 6. The tachometer configure tool allows you to sense a motor through one single revolution to find out the pulses per final drive value.
Below are a some shots of the TMP-LED and TMP-2 temperature monitors :

 

In order to use the tachometer on the Swift I placed a magnet into the main shaft locking ring as shown below. I tie wrapped the sensor to the top of the frames facing the magnet with about a 1mm gap. I used a 3.5mm drill to make the hole in the shaft locking ring and some 5 minute epoxy to glue the magnet into the hole. This is also shown in the pictures below. I have also included a picture showing where the sensor connects to the DPR-100 and some pictures of the supplied magnets.

 

The recording device is quite small in size and ample mounting space can be found in the Swift canopy. Fitting a Swift canopy can be a bit of a fiddle and it was for this reason that I changed the default recording trigger as the two second delay was too short and recording was starting while I was still trying to get the canopy back onto the Swift.

Once the device is installed and stowed away in the canopy its presence becomes unnoticeable. Certainly it's small weight has negligible effect on the flight characteristics.

Graphs

In order to illustrate the data that can be gathered from using this device below are some graphs showing the amps/volts and also RPM monitored during some test flights.

 

Looking at the "RPM monitoring" chart you can see that the RPM figures make the volts and amps readings difficult to see. The software allows you to set a multiplier on the RPM of 10x or 100x in order to make the data display in a more readable format on a single chart. See below where I have now set the RPM to the 10x setting:

 

As well as cataloguing the mission data this software also extracts the maximum and average values for current and the max, min and average for voltage. Max temperature and average temperature are shown for the two temperature probes. Maximum power and average power in watts is also calculated and displayed. Added to this the software also shows the battery efficiency, mah of charge used and the total time of the mission. An example is shown below :

As can be seen in this example the mission data spans a total of 13 min's 55 seconds. The DPR-100 was sampling at 8 samples per second. Total charge expended was 4014 mah and battery efficiency was measured as 72%.

The rest of the values are fairly self explanatory.

The graph in the main view can be zoomed in and out to look at the data in finer detail as well as being able to be saved as a tab delimited file for loading into a spreadsheet.

Conclusion

OK, so that's the basics of it's function and usually the question is does it work and is it any good?

Well, I am certainly impressed, the data this device gathers is superb and it is so small as to be able to be added to a Swift without much difficulty. Ease of use couldn't be simpler and the connectivity and graphing software is first class.
I will be using this device extensively on motor tests to give true in flight data and the examples of this can already be seen on the site.

The new additions of RPM monitoring and live mode add extra diversity to the function of the DPR-100 and it now represents a test bench type device as well as in flight data monitoring. This is an interesting departure from just in flight data and puts the DPR-100 into the same market as devices such as the Power Analyser from Medusa.

If you want a closer handle on your packs efficiency, motor current draw, pack voltage delivery capability etc etc then look no further. This is a highly recommended piece of equipment. I found nothing to concern me regarding it's function and the data it gathers is invaluable in determining the best setup of your machine. Overall a reliable and easy to use product that does exactly what it says it will do. The only missing option for me is the ability to export the graph views as these are often shared online and it would be nice to be able to save the data in a graphical format for discussion in the various forums.