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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: Multiple Parallel Charging!
16/11/2010 20:22:49
 
It’s all down to the 'Potential Difference' (PD).
 Even with one battery discharged down to it’s safe minimum level of charge and with the others part discharged the PD between them will not facilitate a high discharge rate.
16/11/2010 19:33:01
 

I fail to see a problem provided all batteries are the same capacity and cell count.

As I see it.
 The charger  will initially start to charge the most discharged battery until it matches the next most discharged battery,  then continue to charge those two until they match the next most discharged  battery etc…etc…then continue to charge until all are fully charged.
 Connected up but without the charger charging  the batteries would balance each other out.
Thread: Fairey Swordfish
12/11/2010 13:42:33
 
Contact Anglian Model Centre for a 60inch  Swordfish kit.
  Traditional  kit (CAP).  £185.
Thread: How to cut a thread at the end of quality piano wire
07/11/2010 21:05:19
 
A couple of points..
Annealing of carbon steel is done out of contact with air, eg.  In pre-heated dry sand.
 
Cooled slowly in air carbon steel is normalised (de-stressed) not annealed.
 
 As a guide when heating carbon steel … the point of carbon alloy transformation is when the steel no longer attracts a magnet. The required hardening temperature is just  higher. This temperature should be held for a few minutes.
 
 To temper after hardening, polish with wire-wool then heat to a straw colour and immediately plunge in cold water and agitate. As a guide, this is approximately the melting temperature of lead-free solder.

 

Thread: Servos that misbehave on a passive Y lead
06/11/2010 19:11:23
 
This is probably caused by the level of decoupling provided within the PCBs of the E-Power  servos allowing unwanted common mode currents to conflict with the wanted signal (shared through the Y- lead).
 When ‘paired’ with a servo from another manufacturer this servo provides the necessary decoupling.
 If this is so, then a ferrite bead threaded on each Red(5volt) cable close to the servos together with  capacitors (1 to 10nf ceramic) connected across the 5volt and 0volt cables(again close to the servos  and with short leads) will provide decoupling through the  series low impedance now provided.
 On the other hand it may simply be a poor joint at the y-leads common 0volt connection.  
Thread: Powering a 35Mhz Rx with Lipo Batteries
12/07/2010 19:02:54
Steve,
 The cores will be OK just stacked.

 
 My view for what it’s worth.. Interference from the switching regulator will appear on both the signal wire (white or orange) and the ground (black or brown) in phase. Hence 'common mode'.
 The wanted signal is differential with respect to ground.
The ferrite choke acts as a potential divider and with the stray circuit capacitance forming the shunt, will drop the unwanted (interfering) voltages across its large series impedance. Wanted (differential) signals will pass.
 ie. The choke only stops the unwanted signals (that have been picked up on the leads) from entering the circuit.
 
An Alternative method.. a ferrite bead on the signal (white or orange) wire and a 10nF ceramic capacitor (short leads) between the signal wire and ground (black or brown) will be  effective although you may need more than one bead.

I’ve not had any contact with RC PCM so am not aware of the actual PCM encoding used but with PCM signals DC stability is critical.

Edited By Brian Parker on 12/07/2010 19:04:12

12/07/2010 15:45:51
Steve,
How deep are the ferrite chokes,
GC only list the inner and outer diameter.
The critical factor is the depth.
 Inductance is proportional to the length of the turns through the ring (ie the depth of the ring) and also the square of the number of turns.
 I suggest (respectfully) that you need to increase the number of turns and perhaps also use larger rings.
 The aim is to increase the series impedance and thusblock the unwanted common mode currents.
 Basically the more turns the better, you can also stack the rings to increase depth.
07/07/2010 15:49:08
Just for interest.
 An easy and cheap way to reduce voltages ( at reasonably high current levels) is to use bridge rectifiers.

  15 and 20 amp bridge rectifier (15x15mm and 20x20mm) about £1 each.
 

  Connect in series to obtain the voltage required. ie. 5 in series will drop a 12volt (13.2volt) lead acid battery down to 6 volts. Bolt to a heatsink if using at max. rated current.
 
Thread: What size Li-Po? Multiplex Fox
05/07/2010 13:32:59
You just need these.

  Four 120mAh (1/4AAA) NiMh cells from 'Component-shop' at 75P each.
Just solder up to make a 4.8volt battery. Make up a couple of spares and fly all day.
Thread: cdi
03/07/2010 19:26:26
Peter,
 As with many imported Chinese items these CDI units probably share a generic PCB across the various ‘brands’. So if you are correct then faulty units could crop up anywhere.
 
However in my experience invariably when two units fail one after the other the true fault remains undetected.
 
Although come the Chinese industrial revolution who quality checks the quality checks?
03/07/2010 15:23:30
Gary,
The noise from the unit shows that the unit is charging itself.
If you have access to a multi-meter you can test the sensor. With power on, the sensor centre wire(usually red) should show the line voltage (usually battery volts or perhaps slightly lower). Avoid shorting out the leads. Use a pin or similar down the sensor plug case to enable access to the centre cable with the (red) multi-meter lead, multi-meter negative lead to battery negative.
If voltage is present, then transfer the pin/meter lead to the sensor signal wire (usually white or orange) and pass the magnet across the sensor. The meter volts will show a voltage rise and fall as the magnet passes if the sensor is OK.
 If line voltage is absent then the cable or the unit is faulty.
 If line voltage is present then the fault is with the sensor.
(I take it you have tested the magnet?).
'Just Engines' supply replacement sensors for about £4.
 I also see from their Web site that they  stock a ‘CDI’ tester for £7.99
Hope this helps, good luck.
You seem to have spread your postings across two threads, perhaps a moderator will consolidate them into one thread.
Thread: crrc pro gf50i engine
02/07/2010 10:02:58
You don’t give any information on any diagnostic testing carried out.
Are you sure it’s the CDI unit that’s at fault. The sensor is probably the weakest link and is easy/cheap to replace if you don’t have facilities for testing it.
Have you tried a replacement spark plug? A plug can breakdown under load conditions but still give a good spark under static field test conditions.
 I take it that carburettor fault/fuel starvation has been eliminated.
To have two new CDI units fail is probably quite rare.
Thread: Spektrum AR500 brownout recovery slow
21/06/2010 17:58:04
Interesting, but..
 Switching the transmitter off then back on will initiate a scan/reset in the transmitter and a GUID scan in the receiver ie. seconds worth of time and considerably longer than just a signal loss and recovery by the receiver.
 In my opinion (for what it’s worth), simultaneous complete loss of signal in both channels in the receiver is very unlikely with correctly orientated dual diversity antenna (as you have demonstrated with your ground testing Peter.)  Plus a model in the air will have higher operating efficiency antenna than when on the ground.
  The ‘Curly’ antenna configuration is probably quite common and possibly OK provided the general orientation rules are followed.
 But it may also be the root cause of recorded failures.
Thread: Motor Kv - the truth
18/06/2010 11:13:01


 
 
He trades as 'nilesinstall' and has several useful items.

Edited By Brian Parker on 18/06/2010 11:14:30

18/06/2010 10:27:31
Still off the actual thread topic (sorry) but..

A useful temperature module for your ESC, battery etc. (Handy also for IC temp measurement). From ebay and much cheaper than you can make yourself. It is also able to measure voltage, is programmable and has audible warning.

Edited By Brian Parker on 18/06/2010 10:28:09

16/06/2010 11:42:31
Peter B,
 The emissions from the motor leads are probably not an issue.
 My posting was in response to the ‘twisted pair’ and ‘twisting the three motor wires together’. Apart from anything else they would probably get rather warm if twisted tightly together.
 
On the subject of cable length between the battery and the ESC.
Consider..., as the capacitor is charged and then discharged the current will be out of phase and leading the voltage. When the capacitor is fully charged, voltage is maximum and current is minimum with minimal power to dissipate.
 However with inductance, voltage leads current, (the exact opposite of the above). Increasing the cable length increases the inductance and so alters the circuit impedance.
 Also by increasing the cable length/resistance (current in phase with the applied voltage) the impedance of the circuit will again be altered.
 
The capacitor will then have to sink more current.

Edited By Brian Parker on 16/06/2010 11:45:33

Thread: Tatty treasures
13/06/2010 14:45:46

 Simon,
Like the valve springs.
Thread: Motor Kv - the truth
13/06/2010 14:38:31
Sparks,
 Just re-read through the thread.
I note your point, but, if twisted, would that not the un-energised wire produce a couple in the phased energised wires as it moved from energised to un-energised throughout the sequence?
Better to leave untwisted I would have thought.
13/06/2010 11:40:37
Twisting three cables together will only be beneficial (in respect to EMI) if they are in balance ie. the sum of the three voltages is at 0volts at any instantaneous measurement.
Thread: Ferrite Rings
08/06/2010 15:17:18
I’m with Timbo,
 Simplified, 2.4Ghz Spread Spectrum operates ‘in the noise’ via ‘Pseudo Noise’ codes and is thus immune to RF pickup via the servo leads.
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