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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: Build your own telemetry sensors.
16/05/2019 23:24:05

I have one of these working on pack voltage, current and cell voltage (3S tested so far), using your second revision board. Some observations:

1. The ground tracks a quite thin. I would normally use 50 thou width for ground, or create a ground plane.
2. The holes for the resistor leads are larger than needed, I would normally use 0.8mm for these and 1.0mm for (square) header pins.

You have a ground wire connection from the main power negative connecting to the board for measuring the flight pack voltage.This can create two ground paths to the ESC. One is along the main power connection, the other is via this connection to the board, through the board, along the ground of the SPort connection to the Rx, through the Rx and along the ground connection of the throttle connection to the BEC of the ESC.
The main power connection will be a very low resistance, although the power connectors (4mm gold shown) may add a few milliohms.

Now I'm guessing a bit on these values but suppose the main power connection is 5 milliohms and the other route through the board and receiver is 200 milliohms (0.2 ohms). The motor current will split between these two paths in a ratio of 200 to 5 (40 to 1). So if your motor is taking 41 Amps, 40 goes along the main connection but 1 Amp will go through the receiver and board.

I would suggest the wire from the LiPo negative to the board is not fitted.

I'll be adding my pressure sensor, although my board is a few years old and has a different arrangement for the connections. As have been testing using a G-RX8 receiver (to a X9Lite using the new ACCESS protocol) I had altitude anyway!


Thread: FrSky Neuron ESC
16/05/2019 15:56:18

Yes, but the FUC-1 outputs inverted serial while the FTDI is non-inverted. The diode is polarised the "other" way round. I did think could we use a FUC-1 then remembered it was inverted!

This is the same principle.


16/05/2019 14:11:29

Testing a FrSky Neuron ESC. You need to use BlHeli_32 on your PC to configure it. The BlHeli program offers several ways to connect. I originally used an Arduino nano, flashing the nano from the BlHeli program.

I have also used an Arduino Pro Mini, connected to the PC using a FTDI type device. I just "told" BlHeli it was a nano an flashed the Arduino then used it like the nano.

Having looked at what the Arduino was doing I came up with this. You just need a FTDI type device, a diode and a resistor. I just tested it and it works fine.



Thread: Build your own telemetry sensors.
09/05/2019 00:11:00

The '328 datasheet shows the internal bandgap reference is between 1.0 and 1.2V, with a typical value of 1.1V.

One way of using this is to use VCC as the reference voltage, but then use the ADC to measure the bandgap voltage, This enables you to work out what the VCC value is and detect if it is lower than expected.

I use this method in er9x for the 9X radio where if the radio battery drops too low, the VCC drops and the actual measured battery voltage appears to increase.


07/05/2019 23:12:44

The maximum operating frequency of a MEGA328 changes linearly from 10MHz at 2.7V to 20MHz at 4.5V. 16MHz therefore needs just under 3.8V, so works fine at 4.8V.


07/05/2019 18:50:34

Be aware that the maximum guaranteed clock speed when operating at 3.3V is 13.333MHz. 16MHz is not guaranteed to work across all devices and temperatures.

There is an option on the MEGA328 to divide the oscillator frequency by 2, and it is recommended to use this in the application firmware if running a 16MHz crystal with a supply of 3.3V.


Thread: Jumper T16
29/04/2019 13:02:00

Yes, I believe all the modules are based on the DIY multiprotocol module, they all run the firmware as available on Github. Jumper did have the wrong chip on the module shipped with the T12. That chip controlled the inversion of the serial data to/from the module, but they should have fixed that.


28/04/2019 22:23:02

BTW, the firmware on the multiprotocol module is open source, it is NOT a Jumper development (any more than the firmware on the T12 and T16 has any real development done by Jumper).

This is part of the reason why the Jumper hardware is lower cost.

The firmware for the module is here: **LINK**

Pascal maintains this, and has done much of the development. If you use the multiprotocol module please consider making a donation to Pascal for all the work he has done (donate buttons on the page in the link above).


28/04/2019 21:52:21

Details here: **LINK**

Yes, with the diode, it does work in a Taranis.


28/04/2019 17:56:31

Try using a different "receiver number" on the Tx. I know, with the S6R/S8R there is a problem with some XJT modules with some "receiver numbers". I suspect it has to do with the module unique ID. Yo may have a similar problem with the 4-in-1 module.

If you are using an unmodified DJT module then the telemetry data is only available on the connector on the rear of the module.I have modified my DJT modules so the telemetry signal connects to the bottom pin of the module connector (via a resistor and with a diode clamp) so the telemetry is available directly.


28/04/2019 00:03:35

The "FrSkyX" LBT protocol in the 4-in-1 multiprotocol firmware doesn't actually do a listen, it just handles the correct data format. I'm not aware of any plans to fix this (and I coded the changes to support the LBT option).

On all the multiprotocol modules I have, I notice the power output when using the CC2500 chip (used by FrSky protocols) is noticeably lower than a "proper" FrSky module. Careful range checking is therefore recommended.

Personally, I only use real FrSky Tx modules for the FrSky protocols because of this.

Note that FrSky are also very unhappy with Jumper as Jumper appear to have basically copied the FrSky X7 (for the T12) and the X10 (for the T16), so taking advantage of all the development work done by FrSky without incurring the corresponding costs.

FrSky provide me with technical data on their radios (under a NDA), to enable me to port ersky9x firmware. I've been waiting over 5 weeks for similar data for the T16!


Thread: Build your own telemetry sensors.
23/04/2019 15:58:55

Just for information, the lower of those two boards matches the "official" Arduino Pro Mini, as seen on the Arduino site. I also note on the rduino site it indicates the Pro Mini has been "Retired"!


Thread: Understanding the numbers....
21/04/2019 01:27:18

Even with the model on the ground, the height of the aerial above the ground is important. The range you get could be significantly different if the aerial(s) are at the bottom of the fuselage or at the top. You could easily by looking at 4 inches or 6 inches, which would make a 50% difference to the range!


20/04/2019 21:46:46

A couple of things (if you are measuring accurately). 90 feet is 27.4 metres. Going 30 metres away is 10% further.
Secondly, and more significant, the range you get is proportional to the height of the receiver aerial above the ground. Depending on where on the model the aerials are, they could be very close to the ground, e.g., on a glider with no undercarriage they could be only 3 inches off the ground, on a power model with an undercarriage, they could be 6 inches above the ground. You would get a significant increase in range with this.

I always do my range checks with the model on top of my flight box, so the aerial height above the ground is about the same for all models, probably about 12 inches.

Also, in your back garden, you may be getting signal reflections that cause the range to be reduced.


Thread: Build your own telemetry sensors.
17/04/2019 19:32:20

Andy: When adding heatshrink, make sure you don't block the holes in the pressure sensor.

If you just want to sense analog voltages, I have a simple project here (uses 3.3V, 8MHZ Arduino): **LINK**.

Looks like I built my vario sensor back in December 2015, after I had written the code for the SPort interface and the millis()/micros() that work without using interrupts so the software serial timing works reliably.


Thread: Sticky throttle
14/04/2019 23:01:03

As I now understand it the switch warning doesn't handle this requirement. There are TWO correct positions for this switch and one incorrect one in this application. The switch warning currently only handles ONE correct position and two incorrect ones.

It looks to me that the switch warning would need to be enhanced to support this.


14/04/2019 15:40:51

Totally confused now!

If the "Switch warning" is set to require SA to be UP, then surely you get a warning if it is NOT UP, which seems to be what you require!


Thread: Who wants a Warbird Replics Hurricane?
09/04/2019 18:50:15

I've just weighed my Hurricane (without flight pack) and it comes out at 6 lb 8.2 oz. The 6S, 3000 battery is around 18 to 19 oz, so I'm looking at 7 lb 11 oz plus any extra nose weight I need!


06/04/2019 20:53:57

Getting close to finished! I've still to fit the pilot and canopy, but the radio and electrics are all in. Just fitted a FrSky MLVSS (specially wired to give pack voltage only), and an FrSky RPM sensor. I already had a FrSky 150A current sensor fitted. All are mounted in the cowling area, as is the ESC. If I need some nose weight, it may as well be useful!

I think I shall go with a 12x6 prop, just got a couple of Master ones and a 3" black spinner. All fitted and working. I did a quick test indoors using s 2S, 3000mAh battery. I had readings of 7.2V, 9.0A and 4450 RPM. I haven't checked the calibration of the voltage reading yet. As I intend to use 6S, I could be looking at 12000 RPM on the 12x6 and around 1000W.

The next job is to check the CofG. Given I've used the larger tailplane size, I'm wondering how far back from the position on the plan, (mentioned earlier in this thread as conservative, nose heavy) I could go. I like "light" for the overall weight! I'll probably put the 6S in and check the weight and starting CofG position.

For information, someone on another forum asked about the MLVSS sensor (normally plugs into the pack balance connector and reads all the cell voltages) and if it would work to just measure the whole pack voltage, wired to the ESC power leads only. I did some tests and came up with wiring 6, 2K7 or 3K3 resistors, one each between the seven connections to the MLVSS. This provides suitable input voltages to each one, and then gives the total pack voltage.

I'll need some stick time on other models before I fly this!


Thread: How to use IRX4+ multi-protocol module with Taranis?
30/03/2019 16:45:07

For information, the Multiprotocol code was updated at some point to do channel mapping and scaling.

This means, for example, you have a default channel order used in the radio (e.g. AETR), with the mixes set to 100%, and the module maps this to the selected protocol. So if you use "DSM" the module takes in AETR at 100% and sends TAER at 80%.

When the firmware is compiled for the module, you specify the input channel order you wish to use. With a purchased module like the IRX4+, this is whatever they have decided to load!


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