My thanks to Bret of BNB Products for the supply of the DPR-50 for review.
The DPR-50 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. The device being reviewed is suitable for up to a 30 volt input and up to a 50 amp current load.
Considering this device is to be used on a trex it needs to be both small and lightweight. 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 :
As previously mentioned this device records 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.
As can be seen from the pictures above I also had the two temperature monitors
sent through to me as well. One of the temperature monitors is just a straightforward
temperature probe, 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 trex).
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. 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 :
As can be seen 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-50
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 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.
Below are a some shots of the TMP-LED and TMP-2 temperature monitors :
The recording device is quite small in size but considering the lack of
space inside a trex canopy it can be quite a snug fit getting both the
battery monitor and the battery into the canopy of the trex. It was for
this reason that I changed the default sampling rate as the two second
delay was too short and recording was starting while I was still trying
to get the canopy back onto the trex.
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 of the trex.
In order to illustrate the data that can be gathered from using this device
below is the graph created from the 450TH review posted earlier this week.
Below this can be seen a test showing the temeperature probes in action.
Clicking on the pictures above will open the graphs in a separate window
at higher resolution.
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.
The graph 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 delimitted file for loading
into a spreadsheet.
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 T-Rex 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 inflight
data and the first example of this can be seen in the 450TH review posted a few days ago.
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.
To discuss this review or ask questions about the DPR-50 in the forum please click here
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