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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: LBT
01/03/2019 15:55:09
Posted by Doc Marten on 01/03/2019 14:31:50:

The way I understand the regulations and the modules is that all new RC Tx & Rx bought after Jan 2015 needs to conform to LBT, now you can only buy JR modules on LBT so if you have a Futaba, HI-Tec or similar Tx which you want to change it is obselete on 2.4 Ghz unless you buy a DFT (non EU) module, in which case you are breaking the law unless you use D mode Rx, so you need to buy new gear which is LBT and is legal and compatible with everything new unless non EU, if you are a JR user and change to using LBT from pre-LBT you need to either change all your old Rx or tinker with them to make them work. Is this okay so far?

LBT is ONE way of conforming to the regulations, but not the only way.

I believe you may still sell non-conforming equipment as long as it was placed in stock before the regulations came into force.

I'm unclear whether the 'D' protocol does conform to the regulations, without measurements of the duration and power of transmissions we cannot be sure if they meet the 10% media utilisation factor or not. Given the DFT, DJT and DHT modules are still for sale, either they should either meet the regulations or they are "old" stock. 'D' receivers should be legal as they only transmit for part of 9mS every 36mS and at, I believe, only 60mW, so meet the 10% MUF.

Even with the LBT firmware in a XJT module, the module supports 'D' protocol. You may need to update the firmware on the radio to allow the 'D' protocol to be selected. An external XJT module (JR type), has switches on the back that enable switching to 'D' protocol.


01/03/2019 12:22:21

With FrSky, a data packet is sent every 9mS, so 111 times per second. With LBT, the Tx listens to see if the channel is "free". If it is it transmits. If not, then it doesn't. Probably, this has no significant effect compared with transmitting regardless as, if the channel is already in use, anything transmitted probably gets corrupted by whatever is already transmitting, so is lost anyway (and probably corrupts whatever is already transmitting!).

It is not illegal to use non-LBT equipment if it was purchased before the regulations came into effect, or was imported before then.

The DFT (and DJT/DHT) pre-date the LBT regulations and don't support LBT anyway. If the DFT module is available for purchase, it may well have been imported a long time ago.

This older type module and transmission (FrSky 'D' and 'V'" is becoming obsolete.

I note that the DFT module costs £23.40 from T9. You might consider purchasing the FrSky QX7 ('only' £103.40 from T9). This includes an internal XJT module, that fully supports LBT.


Thread: S6R receivers
20/02/2019 23:44:34

I've just put my 'scope onto the outputs of a S8R and can confirm there are no pulses output at power on (except for a single, very short pulse of about 15uS) until the Tx signal is being received.


18/02/2019 23:12:31

Not seen that before! Please confirm you are only turning off quick mode, rather than disabling stabilisation altogether.

My S6R is in a model, so I'm testing with a S8R, but that works fine.
There is a known problem with some XJT modules where the SxR binds but doesn;t respond to the Tx. The solution there is to use a different Rx number. You could try doing that and seeing if the S6R responds i quick mode.


18/02/2019 18:37:24

Sounds like you haven't run the "Self Check" and set the servo limits in the receiver. You need to run the self check for the receiver to "learn" straight and level, then you move the aileron, elevator and rudder controls to their limits (don't have dual rates enabled) to "teach" the receiver the servo movement limits to avoid it over driving the servos.

Do you have the full manual? It is available here: **LINK**.


17/02/2019 12:32:55

My logic says auto-level mode will be fine. The Rx uses accelerometers to detect when the model is not in the level position defined in the self check. It will apply a correction, to the current servo positions, to try to bring the model level. If you have trim applied to get the model level, then the Rx has nothing to do!


Thread: One receiver different models
13/02/2019 19:23:04

If using ersky9x or openTx firmware, with FrSky 'X' receivers, when using "custom" failsafe settings, the settings are held in the Tx and sent to the Rx regularly, so even these are not in the Rx.

As far as plugging and unplugging connectors is concerned, it will depend on how much gold plating is on them, but typical ratings are between 100 and 600 cycles.


Thread: Who wants a Warbird Replics Hurricane?
11/02/2019 18:49:38

It's been in the paint shop!




Insignia are hand painted!

At the moment the canopy is just placed in position.


Edited By Mike Blandford on 11/02/2019 18:50:46

Thread: PIC Programmer
06/02/2019 16:58:11

I'd suggest going the Arduino route to start with. By getting an Arduino Nano, all you need to get started is the Arduino IDE (free download as mentioned) and a USB cable to be able to flash the program (called a sketch for Arduino).

I have used both PIC and Arduino and I think you will get started quicker using the Arduino.

While Phil is correct that assembler is more efficient for real time applications, I find the GNU C compiler (used by the Arduino IDE = "Integrated Development Environment" compiles the code and approaches pure assembler. The Atmel AVR processor (used on Arduinos) also executes code "faster". For the same clock, many PICs use 4 clock cycles for one instruction while the Atmel AVR processor only uses 1 clock cycle for most instructions.
Many PICs operate at 4MHz, so only execute one instruction in 1uS, while most Atmel AVR processors run at 16MHz or more, so execute 8 to 16 instructions in 1uS. If the compiled code is less efficient, the processor compensates. This is a simplified description, as some PIC instructions may need 2 or three instructions on an Atmel do do the same function,but I have looked at the assembly language produced for the Arduino and can confirm it is quite efficient.

John: Being a bit pedantic here, but assembly language is "assembled" while higher level languages (e.g. C, C++, Pascal etc) are compiled.


Thread: Arduino project - Servo Exerciser - RCM&E Dec 2018
04/02/2019 16:54:22

Just using a 8-pin chip is not really good enough for real control functions, although fine for exerciser functions. The reason is the 8-pin device is using an internal clock generator that is not accurate enough to give reliable results as the temperature and voltage changes. You need a clock controlled by a crystal (or resonator).

When I wrote the code, I assumed you would want either the slow function of the reverse function. In each case, sub-trim is easily handled on the Tx. I have, however, added the option to reverse the slow output!

I would not recommend using an analog input, I assume controlled by a pre-set pot, to adjust the sub-trim, particularly on an IC powered model.

You could adjust the centre position of the reversed output in the code. The reversing operation is done by taking the input pulse, subtracting 1500uS, changing the sign then adding the 1500uS back on. This is actually done by just subtracting the input pulse width from 3000uS, you get the same answer.

To adjust the centre position, just add an offset to this calculation:
CENTRE_PULSE_TIME * 2 - ServoPulse

CENTRE_PULSE_TIME * 2 - ServoPulse + ( SLOW_ADJUST_SCALE * offset)

where offset is in uS.


02/02/2019 22:31:17

It must be later already!

Github updated with a switch output on IO2 (also on the LED output to help see it operating).

There are some defines near the top of the sketch where you define the switching point and the switching level. I've also allowed for some hysteresis to prevent the switch output "jittering".

I haven't updated the wiring picture (yet).

Only one of the outputs is slowed at present.


Edited By Mike Blandford on 02/02/2019 22:32:03

02/02/2019 20:02:28

Code and a picture showing the connections are now on Github here: **LINK**

I've now tested this on both a 5V, 16MHz Pro Mini and a 3.3V, 8MHz Pro Mini. A hardware timer is used for input capture and both outputs, so there should be no jitter.

No doubt we could add some enhancements later.


Edited By Mike Blandford on 02/02/2019 20:03:48

02/02/2019 16:18:39

I have a sketch working on a 5V, 16MHz Pro Mini that measures an input servo pulse and outputs it reversed on one output and not reversed but slowed on a second output. I'm just adding an option in the sketch to reverse the slow output.

This should also work on a 3.3V, 8MHz Pro Mini, I have still to test it.

Currently, the slow time, from end to end, is set as a number of seconds in the sketch, fractional parts of a second are allowed. The code measures the time between input pulses and adjusts the slow movement to match.

The operation is to receive an input pulse and then generate the output pulses, if no input is being received, then no output is generated.

I now need to decide where to put the sketch code to make it available. Probably I'll put it up on Github as that is where all my other released code resides.

Arduino (Pro Mini) code I currently have there:

SportToHub - convert FrSky SPort sensors to the old hub format for the 'D' receivers.
SbusToPpm - 16 channel SBUS decoder
APM_Mavlink_to_FrSky - Convert Mavlink telemetry data to FrSky format


02/02/2019 00:22:43

I've got most of the "building blocks", so I'll see if I can knock something together.

For things like a servo reverser, I usually use all my own code, no Arduino library code, so there are no "surprises" caused by code I don't know, for certain, what it is doing!
The downside is the code may be less clear what it is doing.


Thread: Who wants a Warbird Replics Hurricane?
31/01/2019 12:18:24

Assuming you like pictures of progress, here is where I've reached. I found an image of the instrument panel, so printed it at the correct size. It is only placed in position as the printer ink was running out so it isn't as good as it will be. I now need to sort the camouflage pattern to be able to paint the top side.





Thread: Arduino project - Servo Exerciser - RCM&E Dec 2018
29/01/2019 23:48:51

The regulator on an Arduino Pro Mini can supply up to a total of 150mA. A servo will very likely consume several times that amount when operating.

In addition, the regulator has a maximum power dissipation of 450mW at an ambient temperature of 25 degrees C. If you put 12V on the raw input, then, for a 5V Arduino, the regulator will have 7 volts across it. With about 64mA flowing, you will reach the 450mW dissipation limit.


Thread: When an update is not always a good thing!!
29/01/2019 18:37:25

As I understand it, there are times when openTx release a new version that causes the EEPROM contents to need to be adjusted. This is only done in companion I believe.

First I suggest you backup the EEPROM in the radio using the "Backup to file" option in companion.

Then you might try installing Companion 2.2.3, read the EEPROM from your radio into it, flash openTx 2.2.3 to the radio, then write the EEPROM back to the radio from companion. Companion may well have updated the EEPROM contents so your SF function is now correct.

I don't use openTx myself (I use ersky9x of course), but this is how I understand it works.


Thread: Who wants a Warbird Replics Hurricane?
25/01/2019 15:23:40

Mine now has all the stringers fitted and is completely covered in transparent film. I've just "painted" it with Prymol so it is ready for "proper" painting. Because the covering is transparent, it doesn't look much different to the previous pictures!

I weight the wing at 44 ounces and the fuselage is 36 ounces, with a 4.8V NiMh battery fitted. All servos are also fitted, so currently a total of 5lb. The motor is 11 ounces, then there is the ESC, receiver and SBUS decoder and paint to add, so I'm optimistic it won't be so heavy when finished.

With motor, spinner, prop and a flight battery the c of g didn't seem to far aft, so I hope I won't need much nose weight.


Thread: Which Watt Meter
21/01/2019 00:35:40
Posted by Gary Manuel on 20/01/2019 23:28:13:

It should be heat generated in motor (i.e. wasted power) = current² x (winding resistance) watts.

It is dependent on current squared, which is derived from W=IV, where V can be substituted for IR so that W = I²R. The power wasted is a function of both voltage and current.

Yes, but the voltage to be used is the voltage in the windings that is caused by the current passing through the winding resistance, NOT the voltage applied to the motor. Most of the applied voltage is opposed by the voltage developed in the windings (back emf) caused by the motor rotating. Using a higher applied voltage (e.g. 4 cells instead of 3), and keeping the current the same means the motor is rotating faster, while dissipating the same amount of heat (maybe a bit more due to higher mechanical losses).


Edited By Mike Blandford on 21/01/2019 00:36:14

Thread: R615X
20/01/2019 21:13:40

My understanding is the R615X is a full range receiver, but the add-on telemetry board that was available (maybe still is) is short range as far as sending the telemetry data back.


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