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600 Class Nitro Helicopters 600 Class Nitro Helicopters manufactured by Align, Tarot, SYMA, Airhog, Chaos, HK and similar.


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Old 05-07-2008, 10:39 AM   #41 (permalink)
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Quote:
Originally Posted by Mercuriell View Post
Any Silicon diode shoud do - they all drop down 0.7v eg 1N4001's
VERY VERY VERY Wrong.
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Old 05-20-2008, 03:47 AM   #42 (permalink)
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Default Make your own Step Down Voltage Rectifier

General Pourpose Plastic Rectifier.
3.0 A, M A F Rectified current.
Vishay 1N5404-E3

http://newzealand.rs-online.com/web/...duct&R=6289473
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Old 01-23-2009, 12:28 AM   #43 (permalink)
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Can anyone tell me if the s9254 can run at 6.0volts or does it really need to be stepped down to 5.1

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Old 01-23-2009, 01:20 AM   #44 (permalink)
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http://www.gpdealera.com/cgi-bin/wga...pgm?I=FUTM0224

Others may have long term experience, but all I know is from the specs. Not rated for 6V.
Will you burn it up or not? FWIW I'm stepping mine down. Cheap insurance, No?
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Old 01-24-2009, 11:01 PM   #45 (permalink)
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Some servos are repeatedly over clocked and as the rumor goes you can run the 9254 @ 6v if it is regulated. I over clock my 8717 servos to 8v but funny how I still won't do this with the 9254. I run a step down on my 9254 servos.
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Old 02-07-2009, 03:07 AM   #46 (permalink)
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Default You may need back-to-back diodes

Depending on what the step-down is far, you may need two diodes in parallel (opposite directions). If the step-down is for a conventional servo, there's no problem. If it's for a gyro, digital servo, or receiver, you may need the back-to-back diodes. Otherwise, you may cause the device to fail to properly reset when power is applied. (And you may get servo movement after power is removed.)

Note: The below mostly assumes the diode drop is for a servo connected to a gyro because that's where I first saw this.

I'll go into detail elsewhere, but the basic issue is this: Devices like digital servos can sit requiring very little power, then suddenly they need a huge burst of power. To ensure the voltage doesn't sag too much when this happens, they have capacitors on their power input.

Without the diode, when you disconnect the battery, but before the voltage drops enough to shut the servo off, current flows through the servo power lead in the opposite direction. Since the servo is not being commanded to move, the capacitors will hold power. But the receiver is still running, so it will draw power from those capacitors. Of course, they'll only last a very small amount of time, and the voltage will quickly drop to essentially zero. When you re-apply power, you will get a clean reset and trigger servo and receiver initialization.

With the diode, the current cannot flow in the other direction. Only the servo is drawing from that capacitor. Since the servo is not moving, it can hold a voltage for a significant amount of time. Digital servos have a 'keep out' voltage range during which they're neither on nor off, and if you re-apply voltage (even after 10 seconds or so) from the keep out range, they may not properly detect a power on and may not properly reset.

The extra diode allows the receiver, gyro, and other electronics to draw off the servo capacitor, and get out of the keep out voltage range quickly.

If you have a diode drop and notice either 'ghost' servo movement after power is removed or unreliable servo operation after power is reapplied, this is your problem.

If your heli works fine, of course, don't run and change it. But if you're putting in a new voltage drop or experiencing these kinds of issues, use two diodes, one in each direction. The 'backwards' diode does not need to carry much current, so a 1A is more than good enough.
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Old 02-07-2009, 09:30 AM   #47 (permalink)
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Old 02-07-2009, 11:10 PM   #48 (permalink)
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This thread was here when it was hard to get Align step-downs. Now they have the new two way ones and they are plentiful. I have made many my own step-down but for my money I think I will just buy them.
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Old 03-11-2009, 09:31 PM   #49 (permalink)
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Im trying to set one of these up using 1N5404 however the diode is only dropping the voltage by .3 V. What gives?
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Old 03-11-2009, 10:26 PM   #50 (permalink)
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Are you testing it under load?
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Old 05-05-2009, 01:59 PM   #51 (permalink)
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Quote:
Originally Posted by Duff View Post
Im trying to set one of these up using 1N5404 however the diode is only dropping the voltage by .3 V. What gives?
Hey Duff I posted about the 1N504 It turned out that the 1N4001 was all that was needed.
I have an RS number: 628-8931 these were inexpensive. I will build a new one with the 1N4001 on the positive feed to the servo and the 1N5404 OR SIMILAR on the negative line. I have found the the Gyro & Servo have neutral problem under normal initialization technique. ( err turn the rx on with the transmitter turned on first err..). As to Joel Katz post about problems and stored power. I have only one diode (1N4001) like the align one and have this problem of offset neutral. There was a way to get around this and it was to cycle the RX power twice on-off-on with time for initialization. But this may not be a fix just a hack as such. It may not even work all the time. Best to use the new design volt drop with return. The Gaui regs run at 5.7 the old align diode dropped the volts to about 5.4.

Last edited by Milde Shag; 05-13-2009 at 03:38 AM..
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Old 06-24-2009, 01:58 AM   #52 (permalink)
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Quote:
Originally Posted by Milde Shag View Post
Hey Duff I posted about the 1N504 It turned out that the 1N4001 was all that was needed.
I have an RS number: 628-8931 these were inexpensive. I will build a new one with the 1N4001 on the positive feed to the servo and the 1N5404 OR SIMILAR on the negative line. I have found the the Gyro & Servo have neutral problem under normal initialization technique. ( err turn the rx on with the transmitter turned on first err..). As to Joel Katz post about problems and stored power. I have only one diode (1N4001) like the align one and have this problem of offset neutral. There was a way to get around this and it was to cycle the RX power twice on-off-on with time for initialization. But this may not be a fix just a hack as such. It may not even work all the time. Best to use the new design volt drop with return. The Gaui regs run at 5.7 the old align diode dropped the volts to about 5.4.
The way I understand it is that both diodes must be in parallel in opposite directions on the positive wire only, and not one on pos and one on neg.

Am I understanding it correctly.

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Old 06-24-2009, 07:03 AM   #53 (permalink)
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Quote:
Originally Posted by jraydoran View Post
The way I understand it is that both diodes must be in parallel in opposite directions on the positive wire only, and not one on pos and one on neg.

Am I understanding it correctly.
No. They need to be pointing the same direction: band toward the output. Diodes only allow current flow one direction, so it you put them pointing opposite directions on the same power wire, only one of them will pass current and the other will just be a brick.
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Old 06-24-2009, 08:15 PM   #54 (permalink)
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Originally Posted by TheBum View Post
No. They need to be pointing the same direction: band toward the output. Diodes only allow current flow one direction, so it you put them pointing opposite directions on the same power wire, only one of them will pass current and the other will just be a brick.
He's right Bum, see what others saying about current flowing back to system from servo capacitors through the second diode. Its got to be in opposite direction and 99% of the time it is just a brick.
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Old 06-24-2009, 10:04 PM   #55 (permalink)
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Originally Posted by DenV View Post
He's right Bum, see what others saying about current flowing back to system from servo capacitors through the second diode. Its got to be in opposite direction and 99% of the time it is just a brick.
I must have slept through the rest of the thread. :o
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Old 06-25-2009, 01:13 PM   #56 (permalink)
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Thank you Gents. Learning alot each day.

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Old 06-29-2009, 12:03 AM   #57 (permalink)
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As IMO one diode flowing current to the servo (red + wire) and the other flowing current back from the servo (diode pointing toward rx on neg - black wire) Not sure if this is correct. Can anyone confirm or correct this!
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Old 06-29-2009, 07:55 AM   #58 (permalink)
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Quote:
Originally Posted by Milde Shag View Post
As IMO one diode flowing current to the servo (red + wire) and the other flowing current back from the servo (diode pointing toward rx on neg - black wire) Not sure if this is correct. Can anyone confirm or correct this!
Despite my earlier misunderstanding, I'm almost positive you don't want the one on the negative lead. It will reduce the voltage of the pulse signal.
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Old 06-29-2009, 02:33 PM   #59 (permalink)
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This is how I understand it.

Click image for larger version

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ID:	103784

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Old 06-29-2009, 06:09 PM   #60 (permalink)
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Quote:
Originally Posted by jraydoran View Post
This is how I understand it.

Attachment 103784
Exactly.
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