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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: bullet connectors
30/05/2018 23:38:23

I use the same, male bullet on the battery positive. I also use short lengths of hardwood dowel (3/8 inch diameter) in which I drill a hole part way through that accepts the male bullet. I then put these over the battery positive connector to help protect from any accidental shorts. I only remove them for charging or when connecting in the 'plane. They are large enough that they don't get lost, I normally slip them into a pocket when a battery is in use so they are easy to find when disconnecting the battery.

Mike

Thread: QX7
29/05/2018 13:16:24

Yes it does only apply to ersky9x. The QX7 does include two connectors on the main board for extra switches, intended for switches on the ends of the sticks. Ersky9x also supports these for extra switches.

Mike

28/05/2018 22:34:24

Just been hacking my QX7!
Regarding extra pots/sliders, the QX7 has a three colour LED in the power switch (red, blue and green). I'm not sure this is very useful, indeed, on ersky9x, I only use the green LED. If the wires for the other two LEDs are disconnected, then those two signals on the connector are available as extra analog inputs, which seems more useful to me!


x7slider1.jpg

x7slider2.jpg

A bit of a tight fit, the slider is fixed using hot glue inside, and I also have a HC-05 bluetooth module just beside it and they only just fit together.

Details of the electrical connections are here: **LINK**

Mike

Thread: Blackhorse Hurricane 46
23/05/2018 18:59:35

To give some importance the the resistance outside the battery and motor, it is quite possible to find the total resistance of the wires, connectors and the ESC to be 20 mOhms (0.02 ohms).

Consider a 3-cell lipo delivering 40A compared to a 4-cell lipo delivering 30A (the same total power). The voltage loss in 20 mOhm for 40A is 0.8V, while for 30A is 0.6V.

Using a nominal 3.7V per cell, this is 7.2% of the 3-cell battery voltage, but only 4.1% of the 4-cell battery. For higher currents, the difference is greater.

Mike

Thread: Suppliers of 35 mHz crystals
23/05/2018 18:50:22

Be aware that you will probably need a Tx crystal that is for your specific transmitter. The way the FM modulation works, usually by "pulling" the crystal to a slightly different frequency, requires the crystal characteristics match the circuit in the Tx.
When I last used 35MHz I was using a synthesised module and receiver (Hitec) so didn't need crystals anymore.

Mike

Thread: Blackhorse Hurricane 46
23/05/2018 17:15:16
Posted by Nigel R on 23/05/2018 15:45:40:

Chris W

I disagree. Higher current doesn't equal higher losses . . .

For that to be true you also then need to use larger wires between the battery and the ESC and the ESC and the motor, probably bigger connectors (so they have a lower resistance), and an ESC rated at a higher current so it also has a lower resistance.

Mike

Thread: FrSky Taranis - user chat
15/05/2018 15:11:09

I've put openTx on the Taranis plus (release 2.2.1) and repeated the latency measurements. Because openTx doesn't (currently) synchronise to the XJT heartbeat pulse, and, in 16 channel mode, only sends one frame to the XJT every 9 mS, there is quite a variation in the latency, slowly changing over time.

The shortest latency I found was 19.3 mS, jumping to 37.3 mS, and the longest I found was 53.9 mS jumping down to 36.1 mS. These are times from control input to servo pulse. With the longer times, sometimes the SBUS output does occur 9mS before the servo pulse, so the 53.9 mS was 44.9 mS to the SBUS output.

Mike

Thread: Dead Lipo remedy?
14/05/2018 15:43:56

I'm just wondering, the OP said the pack registered nothing on a multimeter. I would have thought even a flattened battery would show some voltage rather than nothing, so perhaps the multimeter never connected to the battery properly. This would mean we don't know how low each cell dropped. It may be the battery wasn't actually too low in voltage, which might explain why it seems to have recovered.

Mike

Thread: FrSky Taranis - user chat
14/05/2018 15:39:17

You probably won't notice the varying latency.

There are 3 parts to the latency:
1. The time between a control changing and the start of sending this to the XJT module.
2. The time to send the data to the module, the module to send it to the Rx and the Rx to send this out on SBUS.
3. The time for the Rx to start a servo pulse.

1. This is random.
2. On ersky9x, this is a fixed time as it is synchronised to the XJT heartbeat. OpenTx doesn't (currently) do this and so may have at least an extra 9mS (randomly).
3. This time is either 0mS or 9mS depending on when the Rx was powered as the servo pulse period is 18mS!

The varying latency is caused by 1. It is 0 to 9mS if the radio sends only 8 channels (or uses the "double rate" I describe), and is 0 to 18 mS if you send 16 channels normally.

In passing, going back to the 27/35 MHz days of sending PPM, the servo pulses were sent in "real time", so zero latency for items 2 and 3, but a varying latency for 1 of the frame time, from 0mS to, typically, 20 to 25 mS.

Using SBUS and either the "double rate" or 8 channels only mode minimises the latency so the variation is only 9mS. Note that if you use a SBUS decoder, it may also only output servo pulses every 18mS for analog servos, but may provide them every 9mS if you use digital servos.

Mike

14/05/2018 12:23:33

I've been investigating latency on a Taranis (plus) to a X8R receiver. The results are posted here: **LINK**.

Note the last sentence!

Mike

Thread: Dead Lipo remedy?
11/05/2018 19:21:51

Simon: What make of battery is it? Maybe it is a newer design that recovers better than older designs.

Mike

Thread: Taranis to Spektrum Trainer.
10/05/2018 10:35:46

By using the method I posted above, (which was the only method at one time) all the required settings are in a model, so it is then possible to create a model in Companion and post it for the OP to just copy to the Taranis.

Mike

09/05/2018 23:23:59

Using the trainer menu is useful as it replaces the normal stick values with those from the student radio before inputs and mixers are processed.
However, for a simple 4-channel model with no special mixes, there is a quick way of just using mixes for the trainer function:

CH1: Ail weight(100%)
R TR2 weight(100%) Switch(SHv) -- A "replace" mix

The first mix is the normal aileron mix, the second uses channel 2 (assuming TAER order this is aileron) from the student radio when the SH switch is active. I don't know for certain with openTx, but with ersky9x, this second mix will automatically become inactive if there is no valid trainer input.

Mike

09/05/2018 18:58:15

Yes you may map the trainer input channels in any order you like. You also have a calibration setting so you set the trainer input centres and also you may scale the inputs. Spektrum tends to only use about 80% of the channel range the Taranis does, so you may wish to scale the inputs by a factor of 1.2 to match.

Only the first 4 trainer input channels are directly handled in the trainer setup, but the trainer inputs also appear as mix sources (TR1 to TR16). They were renamed recently from PPM1 to PPM16, but still appear (in Companion) named PPM1 to PPM4 in the trainer calibration.

You also need to use a special function to assign a switch to swap to using the trainer inputs. You also have the option to pass only some of the 4 main inputs, so the instructor could, for example, keep control of the throttle while passing the rudder, aileron and elevator to the student.

In passing, in ersky9x firmware I have 4 "trainer profiles" available, so if you do a lot of instruction you may have the trainer setup for 4 different student transmitters, and simply select the one you require.

Mike

Thread: Throttle cut button - why the bad press?
03/05/2018 11:57:08
Posted by Martin Harris on 03/05/2018 10:50:27:

. . .sticky throttle systems are brilliant but rely on relatively complex programming - not everyone has the ability to program them or even follow a set of instructions.

Which is why, on ersky9x firmware, I have a "Safety switch" menu where you just select the "Sticky" type and set the controlling switch and output value for the throttle channel, no complex programming.

Mike

02/05/2018 17:24:44

I also use a throttle disable switch with electric, and have for many years. It is automatic for me to switch to the "safe" position before handling a model. Specifically, I use a "sticky" throttle disable, where, once disabled, it doesnt allow the throttle output to change from minimum unless the throttle stick is moved to minimum, so if the throttle stick gets knocked, and then the switch is changed to "enable", the motor still won't start.

I have this in ersky9x firmware as a simple "safety switch" selection, but it may also be implemented in openTx with some logical switches and special functions.

I'm curious regarding a club insisting that the battery is not connected until you are at the flight line, how do you deal with range checks when the radio needs the battery connected?

Mike

Thread: Companion2.2 - Taranis X9D anomalies
02/05/2018 17:09:12

Check in the radio settings that LS and LR are set to "Slider with Detent" as opposed to "None".

Mike

Thread: Who wants a Warbird Replics Hurricane?
30/04/2018 16:52:50

Making slow (by possibly steady) progress. I've bolted the wings on, the retratcs and flaps are complete, except for linking the outer flaps to the inner ones.
All the servos are in. and the weight at present is around 60oz.

h1.jpg

h3.jpg

h4.jpg

h2.jpg

Rather than use the dihedral braces, I've opted to use fibreglass cloth and resin to join the outer wing panels to the centre section.

The outer flaps have a 3mm dia carbon tube at the front, with a 2mm carbon rod inside that extends beyond the flap to form the hinge.

Mike

Thread: Battery problem
21/04/2018 22:06:39

I agree to not charging lipos unattended, but where are you getting information from regarding NiMhs?

Many devices have inbuilt NiMh cells that are on continuous trickle charge e.g. cordless 'phones. They don't say "don't charge overnight"!

A 2500mAh NiMh may be charged at 250mA for 24Hr, at 70mA they will be fine for months. From flat at 70mA they will take around 36 hours to fully charge.

Mike

21/04/2018 18:28:25

Mistreating in what way?

Low current trickle charging is fine, and doesn't damage NiMh cells. For example, I just checked a datasheet for a 1100mAh AAA cell. This specifies you may charge at 45mA for a year continuously! As I mentioned above, only using a "smart" charger will lead to cell imbalance over time, so then you will need to do a trickle current charge to balance a pack.

Mike

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