|Jun 28, 2010, 07:55 PM|
The Quanum telemetry unit - a useful idea: Part1
There’s been a thread started by cryhavoc38running called, “Picked this up at the post office last night. The Quanum 2.4ghz lipo telemetry unit” at
There’s another one here as well with some discussion.
Rather than sidetrack those threads which is where folks are sharing their experiences with this gadget I thought I would post a mini review with some test numbers and hope some people will be encouraged to buy one.
Why? Because this is potentially the most useful “gadget” for electric flight since the Emeter in my view. Not perfect yet by any means, but still uniquely useful.
If you spend any time in the battery discussions, you will know that modern LiPos have just about rendered the traditional low voltage cut-out (LVC) useless. The LVC circuit in the speed control will disconnect the battery from the motor leaving you with just about enough power to keep the Rx going for you to get back on the ground if you are lucky, but they do nothing to protect the battery from excessive drain. There’s often a lot more opinion than good sense on battery forums, but if you pay attention to the guys who really know what they are talking about like NipponDave and everydayflyer the advice is unanimous. Never run modern Lipos down below 3.4V AND only take out a maximum of 80% of their capacity if you want them to live long and keep performing. Most LVC go down to 3.2V or thereabouts and because of their flat discharge curves current technology LiPo’s are for all practical purposes fully discharged at that level. That’s why careful battery guys time their flights and land with 20% time left. But timing relies on an average current drain. If you vary your flights a lot it’s not very accurate.
I’ve always thought what we really need is a “Flying Fuel Gauge” (or Flying Gas Gauge if you live in the US). Something with a current sensor that transmits to the ground the actual mAh taken out of the battery in real time so you would know EXACTLY what was left in the tank. I built a crude one a few years ago using a Hall effect sensor and analog circuits but this is a natural for a microprocessor and 2.4GHz wireless. It’s precisely what the new V2 of the Quanum does. There are some other airborne dataloggers that do the same thing and some newer radio sets have data link capacity built in but there is nothing at this price point that can be used in addition to your regular gear.
V1 of the Quanum was a transmitter that plugs into (and is powered by) the balance lead of your flight pack, which conveniently has nothing else to do while you are airborne. It transmitted the individual cell voltages of the pack continuously. Nice idea but in practice, unless you are tuning your power train with the help of a buddy, pretty useless. As people have pointed out elsewhere, spending your time staring at a complicated set of voltages when you are supposed to be flying a fast moving dot in the sky moves the odds dramatically in gravity’s favour. Even worse, by the time you noticed the (hard to read at a glance) voltages or heard the stupid 3V buzzer it was too late for the health of the battery.
Now they have added a decent current and temperature sensor it is a whole different story for the battery - although there is still significant room to improve the human interaction bit.
It’s dead simple to use. You need to attach your favourite connectors to the current sensor unit using heavy gauge wire (Deans will solder on directly because of the way the board is designed). Then put the sensor in-line between the battery and ESC, plug in the temperature sensor if you want it, hold down the BIND button if this is the first time of use, and plug in the balance lead to the pins on the end. When the LED starts flashing, let the bind button go. Just like a 2.4GHz radio binding should only need to be done once. Then hold down the bind button on the receiver, hold down the power button, and then let the bind button go when the intro screen appears. That’s it. From then on just plug in the Tx and turn on the Rx. If you get a “no signal” at any time just jab the bind button on the Rx and it will search for its Tx. The bind button also toggles between the two Rx screens. The first screen shows the pretty, but useless, bar graphs of cell voltage plus cell voltage, battery voltage and current readouts. The second has all the same info but adds a more precise current reading, temperature (of the battery if that’s where you stuck the sensor) and most importantly the mAh taken from the battery so far. So if you have a 3000mAh flight pack, and the reading gets to 2400mAH you have exactly 20% left.
The attached pictures from HobbyKing’s web site show you what it looks like. As far as I can tell Quanum has become a HobbyKing house brand so I suspect you can only get it from them – happy to add a link to other suppliers if anybody knows of them.
The link to the product is
UPDATE: The biggest problem most people seem to have had with the Quanum is getting it to do the initial bind. Seems that the binding routine in some units with components that may be close to their tolerances is a bit flaky.
If you follow the instructions and it just sits there saying "binding", then:
1) Try moving the Tx and Rx further apart.
2) Also sometimes if you just leave it for long enough it will finally get there. Even overnight!!! See posts 494, 498
|Jun 28, 2010, 07:55 PM|
The Quanum telemetry unit - a useful idea: Part2
So how well is it made and does it work?
The Quanum web site is here but contains reference to V1 and has no more info than is on the box.
The design is sensible enough. The 16g Tx is a narrow PC board with end pin connections and has a standard Duck antenna connected by a proper SMA connector. A lot of the weight is in the antenna. They also make a flexible version which is a bit lighter and I have seen one report it has better range. The Rx is a neat light plastic box, which comes with a clever little clamp (see picture of the Attachment Bracket) to fasten it to your normal Tx aerial. It works on both the thin metal 35/36/40/72MHz telescopic aerials and the thinner part of the base of modern 2.4GHz aerials. It weighs very little, fitted neatly on all my Tx (both kinds) and was easy to adjust the angle. However Iím no RF expert but I would be very wary of attaching anything, much less another powered 2.4GHz device to my 2.4GHz Tx aerial. I think this thing is much better strapped to your wrist where you can glance at it when necessary and not be distracted otherwise.
I havenít been able to find any reliable specifications and someone who has access to the right test gear might be able to post what the data rate and the packet for the link is. I have attached four diagrams which show the Quanum working with my Spektrum Tx. It looks like it uses the same DSSS approach as Spektrum with only a single frequency. Certainly I tried switching both on several times and they always came up on different and discrete frequencies. Reports on the forums from folks who have been flying with it, say it works without a hitch so Iíll just concentrate on the accuracy.
Anyone with other flight experience please post their observations.
The one construction weakness is the tiny push button switches used for binding and power. On the Rx they are acceptable because they are internal and protected from excessive force by the plastic external buttons and should be OK. Donít take the Rx apart though or they just fall to bits. The Tx Bind push button is exposed to ham-fisted modelers and I suspect will be the cause of a lot of failures. The heat shrink acts to hold it together but if you take it off or push too hard there is a real risk of damaging the tiny switch. There are a number of stories of binding problems as well as an example of the switch getting detached on the forums already.
The four attached pictures show the construction of the Tx and Rx with the HS/Case removed. You can see how fragile the push button switches are. Note also both devices have the 6 pads for in circuit programming of the micros but all the important part numbers have been ground off. If you can figure out what they are and you have the smarts you could probably reprogram this thing.
|Jun 28, 2010, 07:56 PM|
The Quanum telemetry unit - a useful idea: Part3
How accurate is it?
It doesn’t matter how clever it is, if this thing isn’t accurate enough it’s a waste of time. There are a number of cheapo Wattmeters out of the Chinese copy factories that are so inaccurate they are dangerous. A meter that lies to you is a menace in my view and often worse than no meter at all.
The easiest thing to test is the accuracy of the individual cell voltages. Using a 40,000count 0.05% accurate DVM I checked the cell voltage over the range 3.3 to 4.2V. The display resolution of the Quanum is 10mV – that is it reads to 0.01V best precision. One cell was within 0.8mV of the displayed reading over that range (i.e. much less than the resolution), the worst was 25mV different. In other words the very worst case was less than 3 display digits out. Perfectly acceptable.
I then measured pack voltage, current and mAh for two discharge rates on a 5000mAh 3S battery. The first was a short run at about 5A discharge to check accuracy at low current, the other a full discharge at 20A. I put the Quanum in series with my EmeterII which was recently calibrated and I know to be fairly accurate. This means the current through both is identical so the mAh should be as well. The voltage measured will be slightly different because of the small drop in the leads.
The x axis labelled “Time” on the graphs is just when readings were made so is not necessarily a linear time scale.
The pack voltages at both 5A and 20A were measured and compared with the Emeter over the whole discharge. They were very close.
Current error at 20A shows the Quanum current plotted on the y axis and the Emeter on the x axis. The black line is what the reading would be if the Quanum agreed with the Emeter exactly. The Quanum reads about 0.8A low at around 20A. That’s 4% error.
This is the one I was really interested in. mAh at 5A and mAh at 20A shows the comparison between the mAh readings of the two meters. I plotted an error graph as before for the 20A run mAh readings. See mAh error at 20A. The actual readings were 4774mAh for the Quanum and 4576mAh for the Emeter which is 198mAh difference at the end of the discharge which took about 13.5 minutes. That translates to a current reading error of 198*60/13.5 = 0.88A. The 5A test gives a higher error but the numbers are low and the test was fairly short.
Conclusion is that the major error with this particular Quanum is in reading the current but it’s less than an Amp for the 20A test which translates to about 4-5% error.
Be nice if it was better but still perfectly usable as an in-flight battery usage gauge. Interestingly, the Quanum shows about a 0.2A current when none is flowing. See picture NoCurrent. The Hall effect sensor used in the Quanum has a much better accuracy than this - it is used in the AEO-RC Wattmeter P1 which is quite accurate - so what would make this thing really nice is a user calibration feature.
|Jun 28, 2010, 07:56 PM|
The Quanum telemetry unit - a useful idea: Part4
The Version2 of this product is usable now as the first available flying gas gauge at a reasonable price (about $80.00 with the current and temp sensor) that you can use with your existing radio gear. It’s accurate enough for the purpose, particularly if you take the time to check the current range with a decent Wattmeter and know what the error is.
It has a great second use as a battery charging monitor. I know you are never supposed to leave LiPos charging unattended, but if they are in a fireproof container in a shed you can plug one of these in and monitor the charge current, actual battery temperature and the total mAh put into the battery from somewhere else in the (warm) house. You need to wire up the connectors on the sensor in reverse since the Hall effect sensor only measures current in one direction but it works just fine through four double brick walls and the inbuilt Rx battery lasts for well over an hour.
This thing could be a lot more useful with a few simple software changes.
1) At minimum, change the silly second screen to show just current and mAh and temperature in BIG letters. That’s what you need to see at a glance when flying.
2) Change the default LV alarm to a more useful 3.4V.
3) Add a user calibration feature for LV alarm and both cell voltages and current. Hold both buttons down for 10 seconds to initiate (would avoid accidental changes and confusing folks who want to use it as-is out of the box). Each of LV alarm, 6x cell voltages and the current would flash in turn for say 3 secs and while flashing you use the Bind or Power button to increment or decrement the value. A final option under this would be to change to a Fahrenheit option on the temperature readout.
I know the cost of changing mouldings is a killer but if a small slide switch could be added to the case of the Rx you could have a RUN and SET position.
Then you could have something REALLY useful if the re-programming could be done.
1 In the RUN position it works as now
2 While it is on, switch to the SET position and a default mAh rating for a battery flashes. While flashing use the BIND and POWER buttons to increment or decrement to set your actual battery capacity. After 3 sec, it moves to a flashing default 20% alarm setting. Increment or decrement as desired. After 3 sec it moves to a flashing default 3.4V Cell Volt Alarm setting. Increment or decrement as desired.
3 Switching back to RUN at any time saves the settings and the second screen then displays %mAh used as a bar graph which flashes when you reach the alarm setting and the beeper goes whenever the mAh limit or cell volt limit is reached.
Be interested in what other folks think and other suggestions.
Quanum, you guys following the forums? Hyperion, Junsi and others have built a strong customer support base and improved their products significantly by talking to users on here.
UPDATE: Someone asked for a picture of how the Current/Temp sensor is connected. I've put that in post # 88
|Jun 28, 2010, 07:57 PM|
The Quanum telemetry unit - a useful idea: Part5
Reserved for updates and links to later posts:
1) It looks like there is full USB chip attached to the USB socket on the Receiver. See pictures in Post #2. For now the socket is only used to recharge the Rx LiPo. Wonder if it will be possible to do firmware upgrades and maybe even PC logging through the USB port in future????
2) And if the USB port is fully functional, it has been pointed out that's the simplest way to set up all the alarms etc if Quanum write a simple software program to do it. See Posts 18 and 19.
3) The current sensor is an Allegro ACS755xCB-100. This is a 100Amp rated Hall effect sensor - data sheet here http://www.allegromicro.com/en/Produ...5/0755-100.pdf
4) Someone asked what range of voltage it will work over. I connected a variable supply via a resistor network to pins 1,2,3 and varied the total voltage between pins 1 and 3. The Quanum gets its power from these pins. The attached graph shows that it will work accurately for a cell voltage from 2.0 to 5.0 Volts. I actually put 6 volts across each cell and it still worked but was starting to do strange things. Do not recommend higher than 5V.
UPDATE: Version 3
Post 120 has an update about V3 which dramatically improves the alarm system, and adds a F option for temperature.
Here's the brief instructions on how to use the new configurable alarms from that post.
It’s all very logical and dead simple to do. The only change to V2 is that you can hold down BOTH buttons at any time for 3 secs and it drops into setting mode. There are 8 screens which you move through with the RH (Power) button. You increment or (or decrement in some cases) the value on each screen with the LH (Bind) button. Everything else works as before. When you have set your preferences, hold both buttons for 3 secs and you are back in operation mode. The Quanum remembers all your settings.
In post 120 I have attached screens shots of the 8 screens – well actually 11 since there are 4 versions of screen 2 when you increment that screen.
If you select the default screen the Quanum uses 6000mAh, 80% capacity used, 19.8V, and Cell voltages of 3.5 and 3.3 as alarm settings.
Unbalanced cell drain issue
The CellLog takes its operating power from Cells 1 and 2 of the battery so on a 3S and above will gradually unbalance the battery if left connected permanently. This is not an issue in a normal flight since the current is only 20 mA or so but it may be if the CellLog is used in a permanent installation where it is connected all the time. If the external current sensor is used the drain is significantly higher at about 70mA. Post # 602 contains useful information about a work around for this.
|Jun 28, 2010, 08:49 PM|
Well, since you are talking about useful ideas - meaning using the Quanum for other than that specified by the manufacturer - here's one:
Use the unit to transmit RSSI value of your receiver.
Refer here on what RSSI is:
RSSI output can range from 1.5 volt to 4 volt, so you'll need a voltage buffer and amplifier in between. I'm sure it'll work, just haven't had the time to do it myself.
Something to think about.
|Jun 28, 2010, 10:36 PM|
|Jun 29, 2010, 03:44 AM|
The Netherlands, LI, Venray
Joined Dec 2008
You know alot of people (like me) of V1 have e.g. not accurate values of cell 4 and 5 reported ( offset of +/-0.2V !!) . So using a 3 cel lipo the readings are accurate.
yes your conclusion is that the major error with this particular Quanum is in reading the current but it’s less than an Amp for the 20A test which translates to about 4-5% error, 4-5% is too much and a new feature of calibration should be implemented.
So i extend your item 2:
2) While it is on, switch to the SET position and a default mAh rating for a battery flashes. While flashing use the BIND and POWER buttons to increment or decrement to set your actual battery capacity.
After 3 sec, it moves to a flashing default 20% alarm setting. Increment or decrement as desired.
After 3 sec it moves to a flashing default 3.4V Cell Volt Alarm setting. Increment or decrement as desired.
After 3 seconds it moves to a flashing current reading offset compensation , Increment or decrement as desired.
After 3 seconds it moves to a flashing cell 1 voltage reading offset, Increment or decrement as desired
After 3 seconds it moves to a flashing cell 2 voltage reading offset, Increment or decrement as desired
After 3 seconds it moves to a flashing cell 3 voltage reading offset, Increment or decrement as desired
After 3 seconds it moves to a flashing cell 4 voltage reading offset, Increment or decrement as desired
After 3 seconds it moves to a flashing cell 5 voltage reading offset, Increment or decrement as desired
After 3 seconds it moves to a flashing cell 6 voltage reading offset, Increment or decrement as desired
And sure the USB connector should be used to upgrade the firmware.
I have another idea what Quanum could be make available is :
Quanum creats a PC program communicating with the USB port so you can do all settings/offset changes explained above in item 2 via this program.
|Jun 29, 2010, 03:59 AM|
The Netherlands, LI, Venray
Joined Dec 2008
So request to all : Spektrum and JR ( no RSSi) , Futaba ( some have RSSI but inside) the next feature of all your receivers add an outside pin available for RSSI value reading 0-5Volt !!!
|Jun 29, 2010, 04:05 AM|
I connected a 6S Lipo (actually two 3S in series with balance connectors joined) and measured all the cell voltages with a precision DVM and compared with the Quanum readout. Did this for LiPos charged and discharged plus A123 to get a set of readings at 3.2, 3.6 and 4.2 volts approx. Did not see any unusual cell 4 or 5 errors as has been reported on V1.
|Jun 29, 2010, 04:12 AM|
There's another problem. It's not that easy to feed a separate 0-5V signal into the Transmitter analog voltage pins. It needs at least two cells "live" to run and if you put the variable signal on another pin you have a common ground problem. Unless the radio receiver ground and the battery ground are isolated (which I don't think is true for most BECs) you end up shorting at least one cell for any configuration I could think up. You could do it if the radio Rx has a separate battery supply of course. You can't feed the signal into the current sense input as that is 3.3V digital logic not analog.
|Jun 29, 2010, 04:20 AM|
Actually that's what I wsa suggesting in my first set of improvements number 3. "Each of LV alarm, 6x cell voltages and the current would flash in turn for say 3 secs and while flashing you use the Bind or Power button to increment or decrement the value".
The reason I put it there was it could be done without any physical change to the unit by adding another switch. Just needs a firmware change.
|Jun 29, 2010, 04:20 AM|
The Netherlands, LI, Venray
Joined Dec 2008
oops you saw it already......lol
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