AR7000 power separation mod

[Chippy]

Found it Thanks
http://www.horizonhobby.com/Products...ProdID=SPM1600

[helinut]

Nice find chippy.
For £3, its a nice piece of mind addition.
Gonna order some now from my LHS (if they art available in the UK yet)

[mac_man]

Cheaper to make your own if there is a Maplins near you and you have a dead servo lurking around. A 4700uF 16V capacitor is only 61p, cut the lead off a dead servo and solder the lead to the capacitor (making sure that you have the polarity right)... cheap & cheerful home made version.

[robgt]

You need to know what the micro farad (uF) rating of this little unit is. I have a feeling it will not be a solution to the receiver reset issue.
The voltage dipping triggers a receiver reset which takes 2 or 3 seconds - ballpark.
If this little capacitor cannot hold up the voltage (through the dip) enough to prevent a reset - it certainly won't keep the power on through a receiver reset...

The DCUP seems to be the answer here as that seems to be able to provide enough power to cover the time a receiver reset takes - plus a bit.

Just a thought...
Cheers,
Rob

[Sesame]

I also like the way the dcup tells you the lowest voltage so at least you can judge whether you need to do anything else to your system.

Mine have been working fine for months but I have no idea how close to shutting down I am.

[robgt]

Mine have been working fine for months but I have no idea how close to shutting down I am.

Same here...
Not for long though - my DC UP is on it's way through the xmas postal system... I look forward to playing with that in about March then
(Then again, this is from Andy, so, tomorrow then )
Cheers,
Rob

[Sesame]

I just ordered up 2 of them the other day. plus a lipo setup which im gonna stick in the knight then I can stick a dcup in each and see how the low voltages compare.
Also gonna try them in a couple of planks but they should be ok as they are fairly low spec servos although in 1 plane there are 6 of them, which were running off a 5cell AA setup, its the same as when I got it but ive not used it at all.

I think they may go into short supply soon lol

[Guest]

Adding a capacitor is not going to solve the problem of the Spektrum Rx resetting
1: The Spektrum operating voltage is 3.5v to 9.6v
If you are running a regulator at 6v / 5A, then that's what comes out of it
So at the Rx bus, if you draw more than 5A then the voltage is going to drop because the regulator is not going to provide more Amps than that and the voltage is not going to rise over 6V because it's regulated
2: If you draw that much current (A) to cause the voltage to drop to below 3.5v, then your capacitor is not going to hold any charge (the capacitor will dumping as soon as the voltage is dropping)

As it's mainly the servos that draw any significate amount of current to cause a voltage drop, then the only way to solve this is to run seperate power bus for the servos

Clarify the capacitor mode:
In AC the capacitor will charge and discharge through the cycle
In DC the capacitor is only going to dump when the voltage required exceeds the voltage supplied

[moyesboy]

On my 450 I have a custom idea lipo alarm
This actually stores data about the voltage from the last flight (20 mins worth I think) and when it is reconnected it bursts the data out of its LED.
There is PC software (free download) and an optical cable to plug into a pc that will then display the voltage trace.

I never spent the money £15 +p&p on the optical lead, but maybe I will.
I set up my lipo alarm so it plugs in with a normal servo plug, so I can use it to see how my volts are holding up on any model.

[Ashley Davis]

If you are running a regulator at 6v / 5A, then that's what comes out of it
So at the Rx bus, if you draw more than 5A then the voltage is going to drop because the regulator is not going to provide more Amps than that and the voltage is not going to rise over 6V because it's regulated

This isn't necessarily true, it depends on the regulator and also on it's power rating. If you exceed the power of regulator (by increasing amps) then the voltage will drop.
Also some regulators / BECs will drop volts as soon as you load them, depending on the design.

[robgt]

If you draw that much current (A) to cause the voltage to drop to below 3.5v, then your capacitor is not going to hold any charge (the capacitor will dumping as soon as the voltage is dropping)

The point of the capacitor is to ensure that the voltage doesn't drop below the receiver reset voltage. As the DCUP has a pretty large capacitor, when the voltage dips, the capacitor fills in the gap keeping the voltage up - the dip will subside, hopefully quickly (unless you have a jammed servo in which case, it's game over anyway) and the system returns to "normal" - capacitor back to fully "charged" and voltage running normally through the receiver.

Thats how I'm reading this at the moment (was going to say currently, but felt a "get my coat" moment coming )
Cheers,
Rob

[Ashley Davis]

the problem with switching regulators (the most common ones) is that they can spike low and high and it only take a nanosecond to trip a reset. So big capacitors such as thos on the DCUP do a great job of smoothing that out and avoiding those trip outs.

[moyesboy]

Got it a bit neater now.
I ran the power to rx through the switch.
Do you need to disconnect the lipo from the align 2in1 to stop it charge leaking the lipo or not?

[SRH990]

I only disconnect the lipo from my Align 2 in 1 to charge it and it's never discharged while connected, same with the Align BEC/regulator on my 600E although there were isolated problems reported with the latter.

[Andy from Sandy]

moyesboy, is there isolation between the -ve of the regulater and -ve of the battery? If they are isolated then you might have a voltage difference on your signal wires to your servos. i.e. your signal wires are not referenced to the common rail of your servos supply. As your system is working it would suggest they are not isolated but it is worth checking.