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Member postings for Mike Blandford

Here is a list of all the postings Mike Blandford has made in our forums. Click on a thread name to jump to the thread.

Thread: lipo battery charger
14/11/2018 23:06:55

Many answers, as usual, to this sort of question.

I got one of these earlier this year: **LINK**

Mains or 12V battery input, two independant outputs and also does the ESR measurement. I also have a GTPOWER A8, so I also sometimes have 3 batteries charging at the same time.


Thread: Which Set Should I buy
10/11/2018 00:29:19

Most of our radios currently don't have the equivalent of a mouse/clicking or a touch screen, so this limits some of what may be achieved. The screen resolution also limits things.

I have made a significant effort to make things easier to find in ersky9x firmware. When you go to edit a model you first get an "index" display where you may select the "type" of item you wish to change:


I'm open to feedback to make this even easier to use.


09/11/2018 22:37:11

Posted by Erfolg on 09/11/2018 20:34:38:

. . .

The one exception that seems to tick all or most of the boxes for me is Frsky. Until it has an intuitive interface, that is not tree structure based, or needs lines of something approaching code, not all the boxes are as yet ticked. Yet no one has a intuitive coloured interface as yet, I believe it will come.

. . .

Perhaps you could define what an "intuitive interface" actually is.
Also, regarding FrSky, are you referring to openTx, FrOS, or something else?


Thread: Returnee to EF seeking advice
07/11/2018 00:50:45

You aren't restricted to openTx on most FrSky radios (and some others as well), you also have the option of ersky9x firmware.

As an example, here is the menu index display (from a FrSky QX7) you get when editing a model. The menus are, in my opinion, easier to follow and find settings than in openTx.


BTW PatMc, my QX7 does have a slider. I added one, and used one of the coloured LED outputs for the switch as the extra analog input. A slider is far more use than three colours for the power switch LED.


Thread: Have I done serious damage.
03/11/2018 19:14:16

If the charger is 500mA, and the battery is 2500mAh, then it will take 5 hours to charge from completely discharged.

If you left it on discharging so it is very discharged, then you will likely find a "Smart" charger will detect a "false peak" very early when charging.

What speed controller do you have in the glider? You may need to configure it for NiMh batteries as it may be deciding you have a 2 cell LiPo and cutting off early when the NiMh voltage gets too low.

Also, what connector are you using from the battery to the speed controller? If one of the Tamiya type like on this battery **LINK** then you should replace it with something more capable as the Tamiya is not suitable for high currents. In my opinion, this type of battery should not be sold with that type of connector.


Thread: TX talking to 2 RX's in different models at the same time?
04/10/2018 09:05:03

David, the "receiver number" is selectable, it is not specifically tied to a "model slot", so you may choose one for each model.


Thread: Autumn is been flying ?
01/10/2018 12:47:23
Posted by David Davis on 01/10/2018 05:41:19:
I managed to land everything on the patch this time so things must be improving! Still haven't got the hang of slowing my landing approaches sufficiently using the elevator. I will continue practising. smiley

Depending on your transmitter capability you could try the following, it depends on your Tx having flight modes with trims specific to each flight mode.

Set up a switch to select "Landing" mode with a unique trim for elevator. Now just (at a good height) switch to "Landing" mode, shut the throttle then adjust the elevator trim to get a slow glide for landing. Makes things easy.

I don't consider this "cheating", I was taught to use the elevator trim (with flaps) on full size for landing.


Thread: Make your bets please Ladies and Gentleman
20/09/2018 20:44:37

YMMV - Your Mileage Might Vary! Almost what you are saying anyway!


Thread: Lipo Battery Storage
19/09/2018 17:01:29

A reason not to store fully charged is "fully charged" depends on temperature. A battery that is fully charged at one temperature becomes over charged at another (I think lower?) temperature.

I store my batteries at storage charge, which is 3.8V per cell according to my chargers. I usually take a charger ti the field with me, so after using a battery, unless I need to recharge it, I put it on storage charge, which usually doesn't take long.


Thread: Battle of Britain Day
15/09/2018 00:21:18

I think he is asking why the "other" thread is titled "Battle of Battle" not "Battle of Britain", with an aside as though from the Polish pilots (in the BoB film) requesting "Repeat Please" as they peel off one by one to engage "bandits".


Thread: Lipo charging
14/09/2018 09:45:16

Dave, that is exactly the circuit I expected.VT13, VD4 and L1 form a buck (step down) switch mode regulator, while VT15, VD5 and L1 for a boost (step up) switch mode regulator.


13/09/2018 22:09:57
Posted by Dave Hess on 13/09/2018 13:45:57:
I can't see any inductors to smooth the PWM. I can't see a reason to do that anyway because charging lipos doesn't need a smooth voltage. The inductor at the other end of the PCB looks like it's part of the buck converter circuit to raise the 12V high enough to charge a 6S battery - probably something like 25V.

The chargers I have use the inductor in both buck and boost modes, converting the supply voltage to that required to charge the battery. They operate using the charge current to regulate the output voltage that is controlled by the PWM mark-space ratio. The PWM frequency used is sufficiently high that the inductor, with the associated output capacitor, produces quite a constant voltage/current, in the same way any switch mode power supply works.


Thread: What gauge wire
09/09/2018 22:13:12

A bit difficult to see exactly what those waveforms are showing, and they don't look much like the ones I got on my digital storage 'scope, where I could capture and "freeze" them.

The ESC outputs are square wave voltage, and the non-driven wire shows a sinusoidal feedback voltage. The current is likely to be reasonably constant as the inductance of the motor tries to keep the current flowing, and the parasitic diodes in the MOSFETs provide a current path.


09/09/2018 17:29:01

The motor, as you have said, includes inductance, in the same way a switch mode power supply uses an inductor. When operating a switch mode power supply in step down mode, the current in the output may be higher than the current in the input, the power in each is the same (except for losses). The same can happen with a brushless motor.

I've just put my 'scope on the wires to a motor. The pwm frequency remained fixed. The outputs to the motor followed a sequence of 6 "phases".

"A" at supply voltage, "B" pulsing low, "C" not driven.
"A" at supply voltage, "B" not driven, "C" pulsing low
"A" not driven, "B" at supply voltage, "C" pulsing low
"A" pulsing low, "B" at supply voltage, "C" not driven
"A" pulsing low, "B" not driven, "C" at supply voltage
"A" not driven, "B" pulsing low,, "C" at supply voltage

On the wire that is not driven, you can see a sine wave, which is the induced voltage in the undriven winding.

(OK, a sample of size 1)

This is as I described.

BTW Kirchoff;s law is for a "node" not a circuit.


09/09/2018 14:40:32
Posted by Focae on 09/09/2018 10:05:14:

Mike, the output current can never exceed input current. A certain gentleman named Kirchoff determined that in one of his Electrical Laws. ‘The sum of the output currents must equal the input current’. You will also never have the same current in two legs of the motor wiring. Outrunner motors are essentially three phase ac motors. The rotating field is created my rapidly switching dc to the legs in turn. The voltage and therefore current in these legs will never be instantly at the dc voltage because the motor windings, being inductors will cause the voltage to rise relatively slowly creating a sinusoidal wave in each leg. Because the windings are 120 degrees apart, you never have all of the current in one leg being opposed by an equal and opposite current in another and you can never have all of the current flowing in one leg. Also consider this, how thick are the wires that form the winding? They are essentially just a continuation of the wires that connect them to the esc. If you did have all off the current flowing in one leg for longer than the ‘average’ switched time, the smoke escapes, usually at the winding because it is thinner than its supply wires.

"the output current can never exceed input current" No, but there are capacitors on the ESC input that provide the "extra" current for the current pulses.

"Outrunner motors are essentially three phase ac motors" No, they are DC motors with electronic commutation.

The ESC connects one of the three motor wires to the positive supply, a second to the negative supply and reads the induced voltage on the third wire to time the commutation.

Yes, the inductance will limit the current rise, but actually sufficiently slowly that the current is essentially constant.

"you never have all of the current in one leg being opposed by an equal and opposite current in another" Yes you do as it is a DC motor, I just described how the commutation is done.

"how thick are the wires that form the winding?" About the same thickness as the wires from the ESC. You may look at the windings and see quite thin enammelled wires, but, for ease of winding and to get more copper in place, the windings are made of multiple, parallel thin wires.


Thread: Horus X10S with Spektrum receivers
09/09/2018 10:09:23

The "patch" is actually to flash the multiprotocol firmware to the module. I created the changes to the multiprotocol firmware so it compiles and runs on the Orange module.

Instructions are available here: **LINK**

The power output may be adjusted in the multiprotocol firmware, the default is +4dbm from the RF chip, then amplified by power amplifier. The RF chip may be set to 0dbm if required.

With the bootloader on the module, you are ablue to then flashit using a FTDI type device, and on sme transmitters you may flash directly from the Tx using a file on the SD card. At present the X10(S) is not one of those as I've not got one so haven't ported ersky9x to it. On transmitters that do run ersky9x, I have added a feature to the Tx bootloader that lets you run an "app". If you are running openTx, you may replace the bootloader with the one from ersky9x, then you get this feature. One of the "apps" available is the one to flash the multiprotocol module.


Thread: What gauge wire
09/09/2018 00:19:22
Posted by Focae on 08/09/2018 09:41:05:

The output wiring from the ESC to the motor does not have to be the same wire size as the input wiring from the battery. The input wires have the continuous current.....the output wires have a switched load so the current is less. . . .

I'm not sure I agree with this!

Suppose that at full throttle you have 30A in the input wiring.
Now you have 3 wires going to the motor, let us call then A, B and C.
For a third of the time you have 30A going out on A and in on B, the next third of the time you have 30A out on B and in on C and the last third of the time you have 30A out on C and in on A.

Yes, the average current in each wire is less, but the current, when it does flow is the same as in the input wiring.

Now suppose you reduce the throttle to have only 15A in the input wiring. The ESC has done this by only driving the output for part of the time. I think you will find you actually have 30A out on A and 30A in on B, but for only half of the first third of the time, and similarly for the other 2 thirds of the time. So the output wires are actually carrying more current than the input wires!


Thread: Horus X10S with Spektrum receivers
08/09/2018 20:13:03

The openTx team are NOT supporting this Tx. The firmware on it has been forked from openTx 2.2, then has a few small changes applied to it. The hardware is a (cut down) copy of the FrSky QX7, with the rotary encoder replaced by buttons, so is running a near copy of the QX7 firmware. The firmware will have been compiled with whatever options Jumper have chosen, you don't get to choose as you do when downloading "official" openTx.

Basically, it seems, Jumper are simply copying the QX7 and the multi-protocol project, both of which support open source firmware. The T12 doesn't add anything that existing radios don't already do.

From a post of mine on RCGroups:

"The patch to openTx is very simplistic, and doesn't have all the conditional compilation needed for the T12 to become another supported Tx. Much more would need to be done, including adding support in Companion, for proper support.
They have basically cloned the FrSky QX7 CPU connections, but left out the rotary encoder and "mapped" four navigation buttons onto the encoder code. This has the unfortunate effect that the "up" button moves up through menus, but then decrements values. There is also no acceleration of changing values, so large changes take a long time. It really needs the buttons handling in the same way as those of the 9X/9XR/9XR-PRO.
I have a T12, supplied for me to port ersky9x to it. I note the following:
1. It is physically quite small, I don't find it comfortable to use (pinching the sticks, not thumbs).
2. There is no momentary switch.
3. The pots on the sides have a lot of movement from end to end, you need several "goes" to move them fully.
4. No SD card was included.
5. The battery bay is sized for 4, AA cells, any LiPo/LiFe battery needs to be quite small to fit. No battery is included. I'm currently using a 2S 1000mAh LiPo, which just fits.
6. On my Tx the audio output is very "tinny". I tried playing some "background" music and it was quite unpleasant! This may be specific to my Tx of course.
7. The display is quite small about 4.8cm diagonal compared with 7.4cm of the QX7. The backlight is not very even.
8. I found the stick spring tension very low, and the throttle friction very weak. I did open the case and use provided adjustments to increase these, but I still find them weak.

The 4-in-1 module included uses the USB port with a USB-to-serial chip inside. This means the USB bootloader doesn't work. The module also has the incorrect chip for the serial inversion (00 instead of 86). This means it only works with inverted serial, and the "Flash from Tx" method has to use inverted serial."

The firmware is likely to be confusing as it includes support for things that are not present, e.g. settings for an internal RF module and haptic.

I do have ersky9x ported to this radio, and will be supporting it, but, as I did with the Turnigy 9XR-PRO, support for the FrSky 'X' receivers and SPort telemetry is disabled unless Jumper reach an agreement with FrSky that these may be included.

From another post of mine on RCGroups:

"A general comment regarding the multi-protocol module. Transmitters use a "unique ID" that is used when binding. Manufacturers produce their own transmitters so that this is unique to each Tx.
The multi module, in most cases, uses a randomly generated ID, so you don't have any guarantee that your Tx doesn't share the same ID as another Tx, either from a manufacturer or another multi module.
DSM protocol is different as it uses a unique value from the actual RF chip, so is guaranteed unique."


Edited By Mike Blandford on 08/09/2018 20:17:31

Thread: Hello
02/09/2018 13:59:07
Posted by Bob Cotsford on 02/09/2018 13:12:05:

Mike, doesn't LBT only affect D16 protocol use?

Yes, but as I said, you may find you cannot select the D8 protocol, particularly on an internal module in a FrSky transmitter.


02/09/2018 13:09:36
Posted by john stones 1 on 02/09/2018 12:22:39:

XJT..can support can support V+D rx's If flashed with non EU firmware, is it this problem ?

I think that is incorrect. The XJT supports 'D' and V-II" receivers whether it has EU LBT firmware or international firmware, I just double checked by binding a LBT XJT to a D8R-II.

Where there may be a confusion is on FrSky transmitters running openTx (and possibly FrOS), if the Tx itself (not the module) has EU firmware, then the 'D' option is not available for selection in the menus.


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