receiver connections

[tailstrike4]

Hi Robert,
I asked Horizon support about what you said, not to connect a power lead from your power expander sport to the BAT/BIND port on my receiver.

Nathan's reply was no it wouldn't cause the receiver to go into bind mode.
He said the only way to get the receiver to go into bind mode is to jump between the negative and signal terminals.

Can your power expander cause a short/jump between the negative and signal terminals?

Thank you
Larry S

[BarracudaHockey]

There's a few BEC's out there that will cause the reciever to go into bind mode, I think Jazz or someone has an offer that if you have one of the affected ones they will mod it for free so it's not unheard of.

[rrritchey]

Hi Larry,
Well, Nathan does not know my circuits so he should not be making assumptions. If he would call me I could explain why this is a bad idea. Here it is in technical terms, I will try to summarize at the end. We use buffer ICs that have CMOS, high-impedance inputs so we do not load the receiver. You do not want an input to the buffer to float, so we put 10K resistors to ground on the wires (signals) that come from the receiver so that if you do not connect a pigtail to the receiver it will be pulled to ground. That means that the signal pin in the BIND plug will see a 10K resistor to ground. The receiver uses some value of resistor to pull the signal wire of the BIND plug up to Vcc, the operating voltage of the microprocessor in the receiver. When you put a BIND plug in the signal wire is pulled to ground and the microprocessor can read this and know its suppose to bind. Now, the big question is, what value of pullup resistor do they use? I have no idea, but unless its smaller than 1K (10 to 1 rule) then my 10K resistor can cause problems. The combination of the two resistors will cause the microprocessor to see a voltage on its bind sense pin that cannot be resolved as yes or no. I have always told people that the PowerExpander and PowerSystem receiver connections are ONLY meant to go in servo slots on the receiver. This is safe. Plugging one of our receiver leads into the battery input on a PCM receiver will put it into DSC if the receiver has DSC and plugging a receiver lead into a Spektrum or JR 2.4GHz receiver "may" cause it to bind.
So, basically the problem is this, while we do not short the signal wire to ground, we do pull it to ground using a 10K resistor. This may put the bind input to the microprocessor in a state it cannot resolve and it may or may not go into bind. I err on the side of safety.

Sorry for all the technical jargon but I wanted to lay it all out there. Technically, I like the way Futaba did their bind, I feel the pushbutton is a safer way. Please let me know if you have any more question.

	Quote: Originally Posted by tailstrike4
	Hi Robert, I asked Horizon support about what you said, not to connect a power lead from your power expander sport to the BAT/BIND port on my receiver. Nathan's reply was no it wouldn't cause the receiver to go into bind mode. He said the only way to get the receiver to go into bind mode is to jump between the negative and signal terminals. Can your power expander cause a short/jump between the negative and signal terminals? Thank you Larry S

[tailstrike4]

Thank you for your response Richard.

So what you are saying is your power expander can cause a link, jump, short, what ever between ground and signal.

Then if I am using all my channels (9) I just don't use the second power lead correct?
I will still have redundancy to the power expander because I have two batteries feeding the expander correct?

I'm now expert on electronics, but I did stay at a Holiday Inn Express last night

[rrritchey]

Hi tailstrike4,
I am saying it may cause the receiver to think it should bind. I am erring on the side of safety since I do not know exactly how the Spektrum receivers are built inside.
We recommend using both power leads into the receiver. You should plug one into throttle and the other into the last AUX on the receiver for JR or Spectrum (first and last servo ports) . On Futaba you would plug into Aileron and the last Aux(again, first and last servo ports). If you have less channels than the PowerExpander on your receiver you should leave on or more of the single lead connections unconnected. This provides redundant power to the receiver. You will always have redundant power to the system if you are using both battery inputs to the PowerExpander.

[tailstrike4]

Thank Robert,

for you explanations you have been very patient with my dumb questions.
And thank you for your support of the St George IMAC contest.
I was there it was pretty windy on Saturday afternoon, only flew one round in the morning then the wind really picked up around noon.
Sunday was a littler better it didn't get windy till about one o'clock.

[rrritchey]

Hi Tailstrike4,
No problem, the clearer I can make things about how my stuff works the better for the user.