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Member postings for Phil Green

Here is a list of all the postings Phil Green has made in our forums. Click on a thread name to jump to the thread.

Thread: Average current draw
09/11/2019 19:09:00
Posted by Simon Chaddock on 09/11/2019 18:54:49:

John

Just remember that whilst the average current draw may be measured in ma the servo peak current can be more than 10 times as much.

Small batteries suffer voltage drop more than big ones. Receivers tend to be more voltage sensitive than servos and the loss of a receiver for just a second (not all recover than fast!) at the wrong time can be serious.

At situation best resolved by a low ESR pack, not by adding another equally poor cell in series
Cheers
Phil
www.4cells-are-enough.com

Thread: How much does an RC hot air balloon weigh?
06/11/2019 22:51:00

sorry Steve, you're right of course but I'd just been reading the CAA's own 'Consumer Registration' page...

caa_page.jpg

Thread: 1s LiPos and receivers
06/11/2019 13:20:44

Banggood do several Futaba-compatible s-fhss micro receivers

Thread: How much does an RC hot air balloon weigh?
05/11/2019 18:13:14

As the regs use the word 'weight' instead of 'mass'... go fly a huge R/C balloon perfectly legally!

Thread: Glossary - your forum needs you!
02/11/2019 18:23:50

In the interests of accuracy could I suggest a few corrections please David, all radio related...

Binding - a process that ensures the 2.4GHz receiver is recognised by the transmitter so the two can operate together. The actual process varies from brand to brand.
This is only true of telemetry sets. With the words 'transmitter' and 'receiver' swapped, it applies to all.

Brown Out - a momentary loss of operation of a receiver due to a drop in supply voltage below a minimum threshold. Normally a momentary effect only, and affects 2.4Ghz equipment rather than the older 35MHz radio.
Actually 'brown out' is a general term describing the unpredictable behaviour of any electronic system at lower than its absolute minimum supply voltage (Spektrum users seem to think its 'their' word)

Crystal - the small component that determines which channel number you fly on. Both tx and rx need to have an identically matching crystal for the radio set to function. 2.4GHz spread spectrum sets don't require crystals.
No, the crystals are not identical and must differ in frequency by the appropriate IF.

FASST - Futaba's 2.4GHz system brand name. Stands for Futaba Advanced Spread Spectrum Technology and uses warp-speed frequency hopping to ensure no breakdown of signal.
Actually FASST frequency hopping is very slow (8 milliseconds) relative to frequency spreading.

Frequency hopping - A system whereby some 2.4GHz radios hop from 2.4GHz band to band many times per second.
No they dont hop from band to band, they hop from channel to channel within the band

PPM - Pulse Width Modulation
No, PPM is Pulse Position Modulation !

Sorry to those who might feel this is pedantic, but surely a glossary is better if its right?

Cheers
Phil


02/11/2019 17:47:18
Posted in Glossary:

Mode 1 - refers to the set-up of the transmitter whereby the left stick operates the elevator and rudder, and the right stick operates the throttle and ailerons.

Mode 2 - refers to the set-up of the transmitter whereby the left stick operates the throttle and rudder, and the right stick operates the elevator and ailerons. Mode 3 and 4 also exist but are very rare in the UK.

Mode 3 - refers to the set-up of the transmitter whereby the left stick operates the elevator and ailerons, and the right stick operates the throttle and rudder.

Mode 4 - refers to the set-up of the transmitter whereby the left stick operates the throttle and ailerons, and the right stick operates the elevator and rudder.

Mode Zero - single-channel operation using no sticks at all - just a button.

Thread: NEW POLL - do you use a throttle kill switch?
30/10/2019 15:23:40

My own encoders have a hardware throttle lock switch which locks the throttle closed regardless of stick position, and also a soft-lock on the stick such that on switch-on, and immediately after the hardware lock has been released, the throttle must be fully closed before it will open.  It alarms to tell you if you're acting against either lock for any reason.  Also, for ESC safety, throttle is the only channel which can't be reversed.

I agree with others who have said that all lecky flyers should use throttle lock. Fingers are very delicate but essential and allowing the ketchup to escape is a Bad Thing 

 

 

Edited By Phil Green on 30/10/2019 15:34:01

Thread: On off switch
29/10/2019 16:43:42

Thats not a good plan Julian, with your new switch "off" your ESC and hence motors are still powered up until you unplug the lipo itself.
As the model appears to be switched off you might well forget and so fully discharge and thus destroy the lipo.

Also its not safe practise to effectively leave the signal input of a powered-up ESC floating, it could pick up noise and spin up.

Cheers
Phil

 

Edited By Phil Green on 29/10/2019 16:47:11

Thread: Life hacks
28/10/2019 11:37:09
Posted by Dad_flyer on 27/10/2019 22:36:54:

Unconventional use of modelling materials.

Always worth keeping a Poundland cyano tube in the first aid box, very good for the 'clean' cuts we tend to get from modelling knives.

Diesel fuel makes very good penetrating oil if you've a rusty nut & bolt or creaky gate hinge

A 3S 2200 Lipo will get your car going if your starter battery is too low to crank - connect in parallel (pos to pos, neg to neg) and leave it for 10/15 minutes before trying

Any more?

 

Edited By Phil Green on 28/10/2019 11:41:16

Thread: PWM Switching rate anybody?
24/10/2019 14:18:54
Posted by John Robertson 3 on 22/10/2019 23:32:27:

Have a look at this; https://en.wikipedia.org/wiki/Pulse-width_modulation#Servos

Then scroll down for a link to: https://en.wikipedia.org/wiki/Servomechanism

and then: https://en.wikipedia.org/wiki/Servo_control

...but PWM as used to position a servo isnt really like PWM used for power control in an ESC
Servo PWM is just a signalling system limited to between 5% and 10% duty cycle at very slow 50cps.
An ESC (and almost anywhere else where PWM is used for power control) uses the full 0 to 100% duty cycle, usually but not necessarily at a much higher rate of several khz.

Also, remember that at 16khz PWM each FET is undergoing twice as many switching operations as it would at 8khz and as we know its the linear transition between off & on that can cause heating in the FETs.

At full throttle, assuming the ESC has been correctly calibrated, the PWM stops and the FETs are hard switched for the full commutation cycle, hence PWM rate shouldn't affect full throttle running

Cheers
Phil

 

Edited By Phil Green on 24/10/2019 22:33:56

Thread: Charging LiFePo4 batteries
22/10/2019 19:05:31

"A123 Systems" put LiFePo4 on the map over 12 years back. My 12-year-old A123 cells are as good as new!

22/10/2019 13:29:27

The difference is clear enough in a written context but you must be careful when verbally speaking to someone about lithium-ion and lithium-iron

Thread: PWM Switching rate anybody?
22/10/2019 11:02:12
Posted by Brian Stevenson 1 on 22/10/2019 06:51:51:
the efficiency at full throttle or near full throttle and thus the flight duration, will go down

Just to clarify, there is no PWM at full throttle, there is only commutation

Thread: Charging LiFePo4 batteries
22/10/2019 10:56:03

In the chemistry menu, most chargers state the nominal voltage, for example the universal B6 and its clones state 3.3v against LiFePo4. Thats the setting you need. The terminal voltage is the critical thing, whereas we're all used to 4.2v for lipos, for LiFePo4's the CV voltage should be 3.6 or 3.65 volts. If you charge LiFePo4's to 4.2v they will be damaged but not with the spectacular results of a lipo overcharge.

Thread: Old 35mHz Futaba
20/10/2019 15:47:38

Personally I think everyone ought to keep at least one 35mhz set, use it or lose it!

Thread: How far do you travel to fly at your club?
20/10/2019 15:38:20

All the slopes I use are over 40 miles away, HoH is 50 plus. Nearest is Baildon, maybe 35 miles, all are well over an hours drive. These are 'each way' distances of course

Cheers

Phil

Thread: Lipo advice please
08/10/2019 19:06:51

My ebike is 10S, two 5S 5000mAh HK Blues. Charge in parallel, run in series.

img_20170314_105814.jpg

Thread: Latest CAA Update
08/10/2019 18:59:30
Posted by UAS.OPEN.040 - UAS operations in subcategory A3:
  • The ‘reasonable expectation’ placed on the remote pilot allows for cases when people unexpectedly move into an area that was previously clear, at which point the remote pilot must take appropriate steps to manoeuvre the aircraft away from these people, or land if this is not possible.

You're slope soaring alone on an isolated hilltop, when theres a voice over your shoulder... "how much does that cost mate?" you cant manoeuvre away from the slope and its much safer to stay up until he leaves 2 minutes later, than to be pressured into an unplanned landing...

 

Edited By Phil Green on 08/10/2019 19:01:03

Thread: Sharkface question
02/10/2019 20:55:17

Your aim should be to launch it at flying speed, a gentle toss is no good !

Ours are all rudder-only, sometimes we have to pulse the rudder to 'get it up on its elbows' as Dave Hughes once said

 

Edited By Phil Green on 02/10/2019 20:55:48

01/10/2019 00:09:06

206.5 grammes ready to fly including 800mAH battery, thats 7.2oz in real money:

206p5grammes.jpg

 

The blue & yellow one in the avatar is just over 8oz, both are film covered.

Cheers
Phil

 

 

 

 

Edited By Phil Green on 01/10/2019 00:17:38

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