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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: Moon landing
20/07/2019 20:02:26

Why do you expect to see a "flame" from the rocket motor? Unlike the Saturn V first stage that uses kerosene, the lunar module uses hydrogen and oxygen, flames are mainly caused by glowing carbon.

For the landing, remember the rocket motor was not that powerful, it was only working against 1/6th of earth gravity. It is also mounted on the descent stage, so is a bit further away from the astronauts than you might think.

It appears that: "Apollo flight trajectories bypassed the inner belts completely, passing through the thinner areas of the outer belts"

Mike

Thread: Phil G's Frame Divider for S-Bus
16/07/2019 21:55:14

SBUS is still 9mS, and I don't expect it to change. Too many users feed it to a flight controller (e.g. betaflight), and want the 9mS rate to minimise latency.

My own SBUS decoder (on Github), using an Arduino Pro Mini, outputs 16 channels, at an 18mS rate. However, If I see a change on the SBUS 9ms after a pulse has been output, I send another pulse to minimise latency, but then revert to pulses every 18mS for a short while before allowing another pulse to be sent "early".

Mike

Thread: S8R stabilisation problemsanyone
12/07/2019 12:33:04

"latest" as a description of the firmware you have flashed is a bit vague! Do you mean the 20190531 version for the S8R?

Mike

11/07/2019 22:56:41

Is the Rx in "Quick mode"?

Mike

Thread: 9XD+
11/07/2019 22:43:38

The X9Lite runs both erskyTx and openTx. The internal module uses the new ACCESS protocol, but this now includes D16 mode. D8 mode is not legal in Europe for new radios as it doesn't conform to the the bandwidth use or LBT.

Mike

Thread: Number of channels?
11/07/2019 14:32:08

Both the X9D+ and the QX7 use an internal XJT module that fully supports 16 channels. For the receiver you either need 2 receivers, each providing 8 direct servo outputs, or you need to use the SBUS output that provides all 16 channels, for which you need either SBUS servos or a SBUS decoder. From a single receiver (e.g. X8R) you still get 8 servo outputs as well as the SBUS, so you may drive 8 servos directly, and only need the SBUS for the other 8.

If you have used an Arduino for anything, I have SBUS decoder code that runs on an Arduino Pro Mini and provides all 16 channels as servo outputs.

For the transmitter you also have the choice of erskyTx firmware as well as openTx. Many users find navigating around the menus, and setting up models, easier on erskyTx.

Mike

Thread: 9XD+
10/07/2019 19:28:59

The QX7 is about the same size as the X9D+.

There is also the X9Lite, which looks very like the X9D+, but is about 0.5 inches narrower. Only £66 from T9, although you will need a couple of 18650 batteries for it. It does have only one POT and 5 switches compared to the X9D+ 2 POTs, 2 sliders and 8 switches.

For firmware you also have the choice between erskyTx and openTx.

Mike

Thread: Understanding the numbers....
04/07/2019 16:50:01

I understand what A, B etc. should be (and are for a Spektrum Rx), I'm questioning whether the Orange implementation is actually reporting the same thing!

With 'B' reporting only 29 "Fades", it seems unlikely to me that there would be 732 actual frame losses. According to Andy Kunz of Spektrum, " A "fade" is when a single antenna does not hear a frame of data. ".

Mike

04/07/2019 11:38:57

I'm wondering if the Orange Rxs are reporting something different to Spektrum Rxs. You reported a 5-minute flight gave: A - 1429, B - 29, L - 0, R - 0, F - 732, H - 0

The 'A' value indicates one antenna missed 1429 frames while the 'B' value indicates the other antenna only missed 29 frames, yet there are 732 frame losses, which I understand is supposed to indicate 732 times where the two antennae received different frames. This may be one received a perfect frame and the other received a bad frame, however the perfect frame will have been used for control!

Mike

Thread: Switching Brand
20/06/2019 11:53:46

In my case I'm using FrSky S8R (stabilising) receivers. These use channel 9 for stabilising gain control, channels 10 and 11 to select mode (normal, stab. auto-level, knife edge and hover), and channel 12 for starting the self-check/ limit setting function. So that's 4 channels needed before any flying controls. Then, on my Mosquito, I have 2 ailerons, 2 throttles, flaps, retracts, elevator and rudder, so 12 in all!

Regarding FrSky transmitters, you may use erskyTx firmware as well as openTx, indeed, the recently released X9Lite is supplied with the choice between the two. erskyTx is generally easier to use, but not really any less powerful than openTx. They were both "forked" from er9x.

Mike

Thread: S6R receivers
15/06/2019 18:28:54

FrSky have posted new firmware for the S6R and S8R receivers.

This fixes the problem with only some RxNums working. It also fixes a problem where SPort data from the Tx didn't "pass through" the SxR.

I've just flashed a S8R (with the FCC version) and tested with RxNums from 0 to 10, all worked. This is with an early X9D+ twhere only some RxNums worked before.

I've also used my "ChangeId" script (on erskyTx), and changed the physical ID of a FAS sensor "over the air" using this S8R. This didn't work before either, or at least changing the voltage on a Neuron ESC didn't work.

Mike

Thread: Forum members' new models: Let's see them.
01/06/2019 21:45:10

Sort of new model. It flew many years ago with a HP61 up front. I've now electrified it, replaced the radio gear and all the linkages. It's basically a (Wolfgang Matt) Superstar although I built the fuselage a bit differently.

Wing span: 62 inches.
Weight: 6lb 13 oz.
Motor EMAX 3526-04, kv 860.
Battery 2 off, 4-cell 3000mAh in parallel.
ESC FrSky Neuron 60.

I tested it in may back garden and got around 65A, so I set the ESC to a current limit of 60A.

(re-)Maidened today, flew rock solid.

superstar.jpg

It flew quite happily on 20A, I only hit full power once, briefly after take off, showed 60.5A at 10900 RPM and 15.7V (so around 950W).
On the second flight the ESC temperature started at 38C and was 76C after 5 minutes and stayed there (don't you just love telemetry and logging?). THe second flight was around 6 minutes airborne and used 1700mAh of the available 6000.

I do have a FrSky S8R (stabilising) receiver in it, but it doesn't actually need it, it was completely stable even with some gusting winds.

I'm using this as practice flying a larger and heavier model ready to maiden my Warbirds Replicas Hurricane!

Mike

Edited By Mike Blandford on 01/06/2019 21:46:38

Thread: Need help to identify plants
01/06/2019 21:22:34

Leave the flowers to go to seed. Eventually you will get some brown "pods" that are full of seeds. You may then collect these and sow them where you want the plants next year.
Or sow them in a seed tray and get some plants ready to put where you want them (been there, done that!).

Mike

Thread: Build your own telemetry sensors.
21/05/2019 19:56:22

David: A bit of confusion, the A3 and A4 here are the FrSky telemetry values being sent, not the A3 and A4 analog inputs to the Arduino.

Chris has solved the problem by setting a scaling value of 0.1 in the configuration file (discussed on another forum).

Mike

20/05/2019 14:51:59

Just change the MVOLT_AT_ZERO_AMP value to 1650:

#define MVOLT_AT_ZERO_AMP 1650 // in millivolt

and you should get a correct 0 Amp result.

Mike

19/05/2019 20:52:21

Andy: It looks to me that you have the pack voltage and the current swapped over in your config files. 47A looks to be what you would get if using 12.2 volts on the voltage input and using the measured value as the current.

Mike

19/05/2019 19:32:56

The output of the current sensor is "ratiometric" to the supply voltage. The value of 40 (mV per Amp) only applies to a supply voltage of 5V. At 3.3V supply, the value is 26.4 mV per Amp ( 40 *3.3 / 5 ).

Mike

18/05/2019 16:31:54

In oXs_config_basic.h I have (comments removed):

#define VFAS_SOURCE VOLT_6

In oXs_config_advanced.h I have (comments removed):

#define REFERENCE_VOLTAGE 3300

// ***** 6.2 - Voltage parameters *****
#define PIN_VOLTAGE 0 , 1 , 2 , 6 , 8 , 7
#define RESISTOR_TO_GROUND 2.70 , 2.70 , 2.70 , 2.70 , 0 , 2.7
#define RESISTOR_TO_VOLTAGE 1 , 4.7 , 10 , 12 , 0 , 18
#define OFFSET_VOLTAGE 0 , 0 , 0 , 0 , 0 , 0
#define SCALE_VOLTAGE 1.00 , 1.0 , 1.0 , 1.0 , 1.0 , 1.0

// ***** 6.5 - Current parameters *****
#define PIN_CURRENTSENSOR 3
#define MVOLT_AT_ZERO_AMP 344 // in millivolt
#define MVOLT_PER_AMP 26.35 // in milliVolt per Amp
#define RESISTOR_TO_GROUND_FOR_CURRENT 0
#define RESISTOR_TO_CURRENT_SENSOR 0

The MVOLT_AT_ZERO_AMP value is first from measurement, then adjusted to give 0.0A (I had -0.3 to start with!).
The MVOLT_PER_AMP value comes from 40 / 5 * 3.293 as I measured VCC at 3.293 volts.

Mike

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!

Mike

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.

Mike

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