Twin receivers

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IAN TURNEY-WHITE
Posts: 31
Joined: December 10th, 2008, 3:02 pm
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Re: Twin receivers

Postby IAN TURNEY-WHITE » February 10th, 2020, 8:35 am

Peter , I fit diodes after the switches on each battery then join the positive wire to form a positive "rail" and ditto for the negative battery wires.
From these two rails, i then fit four supply leads which plug into the receivers , ie. two into each receiver .
This means that both receivers will carry on working if you loose a battery , or a switch or a power lead to one of the rx , or an open circuit diode fault.
If you get a battery fault the diodes prevent the good battery draining into the faulty battery .
On my large models I may have four batteries and six rx power input leads to share the power loads from several large servo,s
I also have a servo operating the choke so that I don't have to reach around a large prop , rather simply operate the choke from a three position switch on the tx , along with a micro switch operated by a servo which cuts the separate battery supply to the ignition.
These two controls are wired so it works on the say rx2 and the throttle on rx1.
Hope the above makes sense , we are after "true redundancy"
Best regards Ian Turney-White

John Greenfield
Posts: 414
Joined: December 5th, 2008, 2:08 pm
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Re: Twin receivers

Postby John Greenfield » February 10th, 2020, 3:37 pm

Hi Ian
I have to disagree that you have "true redundancy" With all 4 batteries connected to just one positive and 1 negative "rail" if you have a servo go short (see previous comments) it will pull the power from all 4 batteries and you will still have a problem.
It would be better if you used 2 rails for positive and 2 for negative and only had 2 batteries on each rail with one pair of rails supplying each receiver.

John

IAN TURNEY-WHITE
Posts: 31
Joined: December 10th, 2008, 3:02 pm
Contact:

Re: Twin receivers

Postby IAN TURNEY-WHITE » February 11th, 2020, 8:58 am

John , I can see your logic with two sets of "rails" , I tend to think in terms of probability , the most common faults being a battery failure ,switch failure or battery lead/connector failure .
Thankfully servo or rx failure is less common , I have only had two servo failures and one rx failure over the last four decades (now showing my age ! )
The servo failures sorted them self,s out , ie. they drew enough current to create enough heat to cause an open circuit in the servo , effectively disconnecting the faulty servo .
For a ground based system fuses could be fitted for say each servo but this is not a practical option for our air borne systems
I suppose its a matter of choice , another recommendation would be to use the excellent LiFe batteries , they have a low internal resistance , for their weight a high capacity and safe to recharge inside the model , also the charging process is much more reliable than nickel metal hydride batteries.
For a 2 cell LiFe ( 2S ) the voltage is around 6.6/6.7 volts which is similar to a nimh 5 cell battery
Ian Turney-White


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