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Member postings for Brian Parker

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

Thread: Motor wire currents
28/01/2010 11:45:51
The action (and current) within the ESC/motor combination is very complicated.
Best not to reduce the wire size, particularly if you intend to increase the length.
Thread: A little comp....
28/01/2010 11:40:59
Yes please.
Thread: Tachometer Question
27/01/2010 16:52:26
It's the lounge light.
 It confirms that it's working OK (50Hz).
Thread: qso's
26/01/2010 14:39:17
Thats just QRP to the Russians, Eric.
They used far in excess of 10MW for the 'Woodpecker'.
Hope you used a long stick for the sausages (and had no spanners in your pockets).
Thread: Part throttle efficiency
22/01/2010 19:42:01
Thanks Martin,
 I've looked at the site, very interesting.
We were trying to find out exactly what was going on in the Battery/ESC/motor setup so as to provide an indication for the best combination for endurance flight.
 As to the FETs its not a case of their inefficiency but the fact that energy is expended (and dissipated) by the fast turn on and turn off rate and by parasitic inductance and  voltage spikes.
22/01/2010 17:21:09
Simon,
Puzzled, you can say that again!
I have (see below) attempted to show the relationship between the three traces.
 

Hope its clear enough to read.
 I did also monitor voltage supply ripple during the experiments. Very little ripple observed. I did think of removing the ESC electrolytic capacitor and observing the difference. Might try this at some stage.
Full throttle, large prop and very low Kv seem to be the indication for endurance together with short leads and the minimum of connections.
Good luck.
 
 
21/01/2010 19:21:11
Calmed things down a little by fitting a 2S lipo.
 'Scope set at 2Volts/Div and 0.2ms/Div at X5magnification.
First set of traces.
 No prop.
Trace pattern is from idle up to a fast idle/quarter throttle.
 Note trace freq/volts at no load.
 

 
 
 
 
 
 
 


 
Second set.
5x5 prop.
The three throttle settings to match the above.
Can't guarantee RPM readings (poor light).
3300RPM 4Watt,
5850RPM 10Watt,
7800RPM 25Watt.
Note trace freq/volts/watts at load.

 



 

 

 
Thread: Airwars system
20/01/2010 17:57:26
 
Peter,
Only if you have the PIC programmer and the project/circuit will benefit from complex microprocessor control and be used in numbers, it will still need to use the IR circuitry. Even then you also need to factor in the cost of the programmer.
In many cases it is simply not needed and a working circuit can be constructed in minutes using a few standard components that can be fault checked by any competent person with the minimum of equipment.
 Surface mounting of components is another ball game.
 
20/01/2010 13:23:45
Linking to the RC system is relatively straightforward.
 Just take it one step at a time.
 

 
For instance..Prototype board for landing/navigation lights.
Circuit will turn on lights and also activate strobe light (equal mark space of 1sec.) when throttle is lowered below a set point.
The circuit will also operate off the Gear switch and could be used for a lost model alarm etc.
The circuit uses a comparator IC to detect when pulses from the receiver fall below a set threshold and then turn on the output stage. The strobe control is a 555 timer IC. But for your purposes you need the 555 IC to drive an Infrared LED (the transmitter), perhaps in 2sec firing bursts. 
The opponents receiver needs its tone frequency matched to the LED's output frequency. The receiver could activate a buzzer or perhaps release a streamer.
 Your opponent needs their transmitter and your receiver matched to a tone frequency different to the above or you could shoot yourself.
 Co-incidentally there was a posting yesterday (I think?) on cable ratings where Bert suggested a link to a web site (Stefan's). Im sure Bert will be around to give you the link again if needed. If you then go to Stefan's Electronic project page there is an ON/ OFF motor controller circuit using the comparator IC almost exactly as I've used above except driving a relay. Just drive the 555/infrared LED from the output instead of his relay.
Use the Gear switch (or a spare channel) to fire the gun.
He even has the PCB layout to download.
You will need a tone controller IC for the infrared receiver, LM567 a few pence from Maplins, plus a 741 op amp IC or similar. The comparator is LM339 (quad comparator under £1 from Maplins).
Pull the relevant data sheets off the web for a wealth of circuit information.
 All this can be built for a few pence.
 
Thread: Part throttle efficiency
19/01/2010 20:52:05
Made up a test rig for a 2812 outrunner.
 Not much success in obtaining a clear and steady trace (budget items).
 Did manage somehow to de-program the ESC though, and have been unable to co-ordinate the beep..beep….beep………….beeps to obtain anything other than wailing banshees. Perhaps the ESC has given up the fight.
 Did have a look at the 'beeps' on the scope, it beeps on one phase only.
 Connected the scope back to the inrunner and ran some tests using the duel trace to show the relationship between the phases.
 Used 2mv/div with X5 magnification of horizontal trace (steadiest wave form).
 The traces with channels Ch1 & Ch2 set at different Volts/DIV is to show the phasing more clearly. Third phase position readily determined from this trace info.
Not enough natural light to obtain RPM.
Pulls around 15Amps at 1/3 throttle and 30+ at full RPM.
First trace 1/3 throttle (unequal Volts/DIV). Second, dual trace at idle. Third, Single trace at Full throttle. Last trace is both channels at equal Volt/DIV.
 

 

 


 



 

Edited By Brian Parker on 19/01/2010 20:53:29

18/01/2010 11:21:36
  Simon,
I did experiment with various time scales but only recorded/posted the set at 5ms.
The problem with fractions of a ms. is holding the 'scopes syncro long enough to take a photo (probably because of the low quality of the ESC) although its not impossible.
The motor tested is a bit of a screamer, so will test a slower outrunner under load and post results, perhaps also including Power, RPM etc per trace.
Might be a couple of days or so before I post results.
17/01/2010 18:05:30
Connected a 'scope probe to one phase of a brushless inrunner (cheapo unmarked 2000kv) powered by a 3S lipo. Motor is fitted to an X-ite wing, prop removed for test. Excuse balsa dust on screen.
 Traces start from a very slow idle, low throttle, high throttle and at max revs.
Scope set at 2volt/div at 5ms/div.
Digest. 


 

I may set up a test rig (to enable connections to be made without the risk of shorting and meltdown of model) and do some proper testing. 
 
Thread: Sad news I am afraid
13/01/2010 14:17:22
Timbo,
Media Player version 11.0.6002.18.111 plays OK
 
The video codec is 9.1 & audio codec is 9.2
Thread: OS .46ax Rear & Front bearings
16/12/2009 09:08:56
A good source for bearings is Bolton Engineering Products they trade on ebay as steve3822.
Also Arc Euro Trade Bearings stock a range in 'model sizes'. 
 Both standard imperial bearings, (the 1-3/32 OD is perhaps not so common)
Thread: Can I go out and play please mummy....
13/12/2009 09:06:30
 
I have vivid memories of a joint ‘parachute jump’ from a barn hayloft using parachutes made from blackout curtains.
The ‘chutes didn’t work...more like free fall.
 We walked (limped) away to play another day.
Thread: MyHobbyStore delivery times
08/12/2009 17:26:11
 
I entered the ‘6th day’ Christmas Advent Draw. My name was drawn out of the hat on the 7th. The prize arrived on the 8th.
How good is that!.
Thread: The Schroeder Spark Engine
07/12/2009 11:33:57
 
For budding engine builders, the Plan and Roger’s Build notes for the Schroeder .09 cu in. engine have been put on the Model Engine News web site.  (Sadly Roger Schroeder passed away in earlier this year).
Link   index December 2009
 
  There are options for ‘Spark’ or ‘Diesel’ on the plan. The engine is constructed from Bar Stock so no castings are needed and all major operations can be completed on the lathe.
 Perhaps not a ‘first build’, but it’s not that complicated just needs care, accuracy and sharp tools.
 Its now on my ‘to build’  list with some modification for electronic ignition, the prop driver and possibly to the two-piece piston.
 Anybody else intending building this interesting engine?
 Currently there tends to be a drift away from glow but a modification to glow is do-able.
Thread: The Cafe
07/12/2009 11:25:41
 

Unless there is more than one Brian Parker then for the first time in my life I’ve won a prize. The  Chair.

 

Thread: Multiple Speed Controllers
03/12/2009 17:51:57
 
Peter,
Nice to see Kirchhoff spelt as Kirchhoff intended.
 Have not used multiple ESCs but if I had and was on 35Mhz I would be wary of ‘noise’ spikes generated through the common return lines not all at a true 0volt.
 
For Anoraks…according to Kirchhoff .… the sum of the currents flowing into a junction in a circuit is equal to the sum of the currents flowing out of the junction. And …. the voltages in a circuit must add up to the voltage applied to the circuit.
In fact ‘One transistor leading the Other ’ in a circuit is used to advantage start the oscillator for the CDI in my ‘Spark ignition’ thread.
Thread: ASP 1.20 fourstroke glow-petrol conversoin
01/12/2009 19:45:59
 
Look forward to your figures.
20:1 is a fairly high (but safe) oil content. Would performance/RPM with a slightly rich 30:1 (or even 40:1)ratio be better than a leaner 20:1 ratio? I don’t know, just thinking out aloud….............
Have you looked in on my thread on spark ignition?
 My results (to date) using a home built ignition system on a 40 two stroke using petrol at 20:1were not as good as your ‘Just Engines’ unit, albeit fitted to a larger four stroke, though my spark ignition performance was more than satisfactory when using glow fuel.  
There is a high satisfaction factor when things go right.
I have several developments in the pipe-line to try out including  the home brew CDI unit.
That is when I have sorted the hall-effect trigger circuit for it.

Edited By Brian Parker on 01/12/2009 19:47:15

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