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New RCXEL 7.4V

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Old 06-12-2012, 08:07 AM
  #26
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Default RE: New RCXEL 7.4V

Someone recently posted a schematic of a RCexl CDI unit in this thread here: http://www.rcuniverse.com/forum/m_11114518/tm.htm

So trying to use more than 6.0v would cause excess current consumption and cause something to overheat and fail. They aren't using heat sinks inside and the tiny suface mount voltage regulator for the microprocessor is only rated to a max of 100ma too. I would bet that the voltage multiplier circuit transistors would be the failure point, but the little HT7550 voltage regulator is not going to like a higher input voltage either. But even the trigger SCR could go out of spec if the input voltage is too high.

It would be interesting to know what the output voltage is on the voltage multiplier that drives the ignition coil primary windings is.
A good hint though is the datasheet for the X0405ME SCR is 200 to 800 volts, max current 4amps. Thus the circuit is tuned for turning 5v into at least 200v to drive the coil with.



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Old 06-12-2012, 09:51 AM
  #27
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Default RE: New RCXEL 7.4V


Those new RCexl CDI units that can handle 6.0 to 7.4v battery packs are very interesting. I'll have to get one later myself. But right now all of my CDI's work really well off of 4.8v battery packs. So there is no need to put one of the new ones in yet.
[/quote]


+1, my thoughts exactly.

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Old 06-12-2012, 11:17 AM
  #28
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Default RE: New RCXEL 7.4V

Like Antique says.... why" re-invent" the wheel !
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Old 06-12-2012, 11:43 AM
  #29
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Default RE: New RCXEL 7.4V


Quote:
ORIGINAL: captinjohn

Like Antique says .... why'' re-invent'' the wheel ! [img][/img]
I don't agree. Where would we be with stone or wood wheels?
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Old 06-12-2012, 03:28 PM
  #30
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Default RE: New RCXEL 7.4V

I think Zenoah recently changed their ignitions so they say they are Lipo ready. I heard their earlier ignitions were power hungry. Has anyone tried their new ones?
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Old 06-12-2012, 05:54 PM
  #31
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Default RE: New RCXEL 7.4V


Quote:
ORIGINAL: thepamster

I think Zenoah recently changed their ignitions so they say they are Lipo ready. I heard their earlier ignitions were power hungry. Has anyone tried their new ones?
They are now RCexl ignitions.

Milton
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Old 06-12-2012, 06:21 PM
  #32
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Default RE: New RCXEL 7.4V

Quote:
ORIGINAL: dirtybird


Quote:
ORIGINAL: captinjohn

Like Antique says .... why'' re-invent'' the wheel ! [img][/img]
I don't agree. Where would we be with stone or wood wheels?
I would not say that was re inventing the wheel, they just improved the concept, then added tyres to make the ride smoother

Karol
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Old 06-13-2012, 10:30 AM
  #33
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Default RE: New RCXEL 7.4V

This is about using better batteries, nothing else really. Servos are going up in voltage acceptance as well to keep up with the times. NiCd batts are a thing of the past, just like dry cells!
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Old 06-13-2012, 10:46 AM
  #34
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Default RE: New RCXEL 7.4V


Aww heck and I have such fond memories of using these dry cells to start my engines many years ago.
The spark ignition engines used to use some AA dry cells to run the ignition system on them many years ago too.
You didn't get too many free flights with them though.







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Old 06-13-2012, 02:01 PM
  #35
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Default RE: New RCXEL 7.4V

Memories, memories.

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Old 06-13-2012, 07:39 PM
  #36
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Default RE: New RCXEL 7.4V


Quote:
ORIGINAL: karolh

Quote:
ORIGINAL: dirtybird


Quote:
ORIGINAL: captinjohn

Like Antique says.... why'' re-invent'' the wheel ! [img][/img]
I don't agree. Where would we be with stone or wood wheels?
I would not say that was re inventing the wheel, they just improved the concept, then added tyres to make the ride smoother

Karol
Problem is ....its not smoother....now if you get the wrong ignition,ya get a strange jump in RPM when not wanted....like on landing !
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Old 06-14-2012, 07:35 AM
  #37
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Default RE: New RCXEL 7.4V

I remember many times not being able to fly because my 1/2 a plug drained my dry cell.
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Old 06-14-2012, 11:10 AM
  #38
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Default RE: New RCXEL 7.4V

Yeah, I remember trying to tape flashlight batteries together, (including the connections) when I was too young to solder! (Never worked too well, but sometimes I got an engine start and a flight out of them.)

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Old 06-18-2012, 02:28 AM
  #39
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Default RE: New RCXEL 7.4V

I would be very pleased if someone could help me. This is my first build of a model with a gas engine. Model A Sbach 342. with SAP 180. I would like to use a Rcxel kill switch. But I would like know if I can use 4.8v battery for ignition. And a 6v for receiver. Or do I have to use batteries of the same voltage, ie 4.8v or 6v. I must say I have no one in my club that help me. As no one else fly gas engined models. Most appreciated if somone can give me an answer. Knife/edge
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Old 06-18-2012, 03:20 AM
  #40
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Quote:
ORIGINAL: Knife/edge

I would be very pleased if someone could help me. This is my first build of a model with a gas engine. Model A Sbach 342. with SAP 180. I would like to use a Rcxel kill switch. But I would like know if I can use 4.8v battery for ignition. And a 6v for receiver. Or do I have to use batteries of the same voltage, ie 4.8v or 6v. I must say I have no one in my club that help me. As no one else fly gas engined models. Most appreciated if somone can give me an answer. Knife/edge
You'll be fine doing that. They do not need to be the same voltage.
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Old 06-18-2012, 09:51 AM
  #41
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Default RE: New RCXEL 7.4V


Quote:
ORIGINAL: dirtybird

I just received a new RCXEL ignition. Its marked 6 to 7.4V. Apparently it has been modified to work with A123's

Its been modified to work with 2S lipo's and anything of lower nominal voltage.

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Old 06-19-2012, 06:31 AM
  #42
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Subscribed...
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Old 06-21-2012, 03:24 AM
  #43
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Default RE: New RCXEL 7.4V


Quote:
ORIGINAL: dirtybird

Quote:
ORIGINAL: MTK


Quote:
ORIGINAL: dirtybird

Correct.
But when you increase the input voltage this no longer is the case.
I am talking about the insulation between the wires in the coil and in the spark plug lead.
Silicone rubber insulation on both of those items. Silicone rubber has one of the highest dielectric strengths of all plastics/rubbers per unit thickness.
OK but everything has its limits.
RCXEL warned not to use more than 6V or eventually the unit would fail.
Why else would a higher voltage ruin a unit?
If the unit produces 40000v with an input of 5v, a 1v increase in the input would increase the output 8000V
The increase is at the input side. How it influences the charging of the capacitor remains to be seen. The capacitor will charge faster, but will the end voltage be higher as well? It is the capacitor end voltage (read charge!) that determines the current (read energy!) through the primary coil and hence the end voltage the secondary coil can produce.

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Old 06-21-2012, 05:18 AM
  #44
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Default RE: New RCXEL 7.4V

Thats pretty much how I understand it. theres no indication that the output voltage is proportionally higher as a result of the higher input.
 
the batteries we are always advised to use start off at 5.8V and drop to 4.8V close to the end of the charge with no discernable difference in engine performance as a result of the dropping input voltage. This would indicate that the relationship of input and output voltage is decoupled.

If the extre energy from the higher input voltage is discipated as heat how significant is that extra heat in relation to the heat from the HV at the output side? I can't see that it is..
Is the extra input voltage simply not drawn and the ignition circuit actually draws a constant voltage that is much lower than the nomimal voltage?
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Old 06-22-2012, 07:13 AM
  #45
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Default RE: New RCXEL 7.4V

Many thanks for answering My question it was much appreciated.
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Old 06-22-2012, 09:05 AM
  #46
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Default RE: New RCXEL 7.4V

In looking at the schematic posted, the capacitor charging circuit it is a free running oscillator/voltage doubler circuit. As such its output is proportional to its input voltage unless a regulator is involved, which would eliminate voltage sensitivity. I see no regulator.
The voltage on the charging capacitor is directly controls the output voltage developed.
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Old 06-22-2012, 10:31 PM
  #47
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Default RE: New RCXEL 7.4V


Quote:
ORIGINAL: dirtybird

In looking at the schematic posted, the capacitor charging circuit it is a free running oscillator/voltage doubler circuit. As such its output is proportional to its input voltage unless a regulator is involved, which would eliminate voltage sensitivity. I see no regulator.
The voltage on the charging capacitor is directly controls the output voltage developed.
Bingo
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Old 11-07-2012, 12:56 PM
  #48
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Default RE: New RCXEL 7.4V

One must wonder why the power to TR1 isnt taken from the output-side of HT7550-1, instead of from the input side......

If the reason is that HT7550-1 cannot deliver enough current for TR1....then, choose another regulator. They are cheap.

Can you imagine how much trouble this has created.....
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Old 11-08-2012, 08:38 PM
  #49
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Default RE: New RCXEL 7.4V


Quote:
ORIGINAL: earlwb

Someone recently posted a schematic of a RCexl CDI unit in this thread here: http://www.rcuniverse.com/forum/m_11114518/tm.htm

So trying to use more than 6.0v would cause excess current consumption and cause something to overheat and fail. They aren't using heat sinks inside and the tiny suface mount voltage regulator for the microprocessor is only rated to a max of 100ma too. I would bet that the voltage multiplier circuit transistors would be the failure point, but the little HT7550 voltage regulator is not going to like a higher input voltage either. But even the trigger SCR could go out of spec if the input voltage is too high.

It would be interesting to know what the output voltage is on the voltage multiplier that drives the ignition coil primary windings is.
A good hint though is the datasheet for the X0405ME SCR is 200 to 800 volts, max current 4amps. Thus the circuit is tuned for turning 5v into at least 200v to drive the coil with.


[img][/img]
I do not believe this is Xu Liangs latest circuit.He has made a few changes for the newer RCEXL HV ignitions. I have the new sch but have not tried it. I am not going to change mine which is very close to the one above.Close hell it't the same.
BCCHI
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