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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: 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.

Mike

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

It's been in the paint shop!

hpaint1.jpg

hpaint2.jpg

hpaint3.jpg

Insignia are hand painted!

At the moment the canopy is just placed in position.

Mike

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.

Mike

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

like:
CENTRE_PULSE_TIME * 2 - ServoPulse + ( SLOW_ADJUST_SCALE * offset)

where offset is in uS.

Mike

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.

Mike

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.

Mike

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

Mike

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.

Mike

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.

hurri1.jpg

hurri2.jpg

hurri3.jpg

Mike

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.

Mike

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.

Mike

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.

Mike

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).

Mike

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.

Mike

Thread: Motorcycles and model flying
14/01/2019 13:38:41
Posted by Dave Hess on 14/01/2019 11:25:07:

I would conclude that it's a complete non-starter to use a motorbike for transporting your plane to the field.

See my post above, I disagree. I regularly used my motorbike for transport, when I was at university, and in the end I took the 'plane in the box home, which was a trip of 104 miles. The 'plane was perfectly OK.

It does need a 'plane designed to fit in the box.

Mike

13/01/2019 23:10:35

I had a Honda 175 with a (sloping) luggage rack behind the pillion seat. I made a wooden "wedge" that clamped to the rack, and provided a flat surface that extended the flat top of the pillion seat rearwards.
Then I made a plywood box that fitted on this flat surface, and extended behind it as well. The box included a couple of bolts on the sides that could be extended down to locate into the wedge to hold it in position. I also strapped it down with bungees.
The box was 1 foot square in cross section and 3 feet long with 2 inch wide slots down each side for wings and a fuselage would fit in the centre, with the tail sticking out the back of the box. Accessories and the Tx fitted under the fuselage. I transported a 60 inch span, 60 powered aerobatic model in it! The "wedge" included a couple of wheels so I could lift it and the box off the 'bike and wheel it to the pits!
As the whole thing was much lighter than a passenger, it didn't actually affect the handling of the 'bike.

Definitely surprised people when I arrived and assembled such a large 'plane and flew it!

If you have a much smaller model, you should be able to do something similar, but would only need a small box for it, say 9 inches square and only 2 feet long.

Mike

Thread: X9D+ Double Trouble
12/01/2019 23:50:23

Two questions:

1. You can't access the bootloader, but does the radio start normally?

2. When you plug in the USB with the power off, do you see a device in the "Devices and Printers" caled "STM Bootloader"?

Mike

Thread: Who wants a Warbird Replics Hurricane?
29/12/2018 21:29:14

I have been "plodding" along with my build. It doesn't look much different, but I have the wing fully covered (transparent, iron on film) and just need to add the linkage to one of the outer flaps. The radiator is also on the wing, so that is all ready for painting.

I have the (electric) motor mounting in place (ply box), a flight battery bay behind the motor with a hatch in the top of the cowl for access. The wing fairings are all in place and the exhausts on the cowl. Under the battery bay I hae a space for a NiMh radio battery (well if I need some nose weight it may as well be useful!). My current plan is to use the BEC from the ESC for main flight controls, and power the flap servo and the retracts from the separate NiMh battery. I may include a (schottky) diode from the battery to the BEC output as a backup supply.

All servos are fitted and operating OK, I put an 8-channel Rx in to test everything. As I have 5 connections to the wing (two aileron servos, two retracts and the flap servo, I shall put a SBUS to PPM converter on the wing to reduce the wiring needed, plugging up 5 cables sounds bad!

Just to see what it looks like, I put a 70mm spinner with a prop on the motor. It seems like I'll need a slightly larger spinner, 80mm looks about right, but as I have the 70mm one I may just use that to start with.

Any one else actually building theirs?

Mike

Thread: Gatwick drone incident
23/12/2018 14:22:01
Posted by Bob Cotsford on 23/12/2018 12:01:07:

Mike, does the R9M module allow for telemetry? Not that using that would exempt your models from being UAVs.

Sorry, slightly off topic.
Yes, that is how I monitored the RSSI, it has full FrSky SPort telemetry, at the lower power levels.

Mike

23/12/2018 11:52:27
Posted by Ronaldo on 23/12/2018 11:05:15:

Hmmm ... well if all else fails, I could always go back to my control line flying days ... They can't put restrictions on that ... or can they ? dont know

From the ANO (2016):

(2) A relevant aircraft which is launched, moored, tethered or towed must not be operated—
(a) in such a manner as to—
(i) represent a hazard to other airspace users; or
(ii) without the permission of the CAA, result in any part of the relevant aircraft whilst it
is being launched or towed, or its tether, mooring or towing equipment, extending
more than 60 metres above ground level;
(b) within controlled airspace or airspace notified for the purpose of this article;
(c) within the aerodrome traffic zone of a notified aerodrome during the notified operating
hours of that aerodrome except—
(i) during the day and in Visual Meteorological Conditions; and
(ii) with the permission of the person in charge of the aerodrome, the appropriate air
traffic control unit or the CAA.

So you already have restrictions on control line as they are "tethered".

David Mellor: I think you will find the 900MHz band is becoming more used as, in some countries, more output power is allowed (up to 1watt), and modules and receivers are readily available. I have the FrSky R9M module and receiver, and could easily update the firmware to use 1 watt power. I tested on 10mW and got similar (or better) RSSI results to the standard 2.4GHz units.

Mike

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