WHATS a UBEC ? and Who Needs Them ?

[GooberRC]

Good idea. I was wondering how I could test that all is well once I've got it hooked up. I'm guessing a good voltmeter is becoming a necessity at this point. I picked up one of these meters the other day, but I can't test voltages going to the receiver with that.

[kyleservicetech]

Originally Posted by GooberRC

Good idea. I was wondering how I could test that all is well once I've got it hooked up. I'm guessing a good voltmeter is becoming a necessity at this point. I picked up one of these meters the other day, but I can't test voltages going to the receiver with that.

There are a lot of decent digital volt meters out there, from $3.95 Harbor Freight units to my two $350 Fluke 87's.

They are available from Walmart, Radio Shack, many automotive places and so on. Any meter in the $20 or so range will be good for what's needed in our electric model stuff.

Just make certain that the meter's battery isn't some $$$$ special unit.

I bought a Etek #10709 meter from Walmart several years ago, its a very nice well made meter for under $20. It's also got a thermocouple type temperature probe. (If you can find one that is)

Take a look:
http://www.walmart.com/ip/Digital-Mu...10709/14521541

[GooberRC]

Thanks Dennis. Unfortunately that particular one was not available but I found what appears to be a suitable substitute on Amazon: http://www.amazon.com/gp/aw/d/B000EV...8974895&sr=8-1

Time to start the build I guess

[GooberRC]

OK Dennis - I'm ready to be graded The first pic shows the diode orientation before heat-shrink, and the second shows the entire setup. Lots of cable to tuck away inside the airframe but that's ok. I decided to go with the modified extensions instead of performing surgery on the ESC and UBEC.

I do have one question - the UBEC has a signal wire coming from it in addition to the +/-. I'm assuming that is for programming access and will be inactive in flight. Should I disconnect the signal wire from the UBEC diode extension just in case?

Oh - one other thing: The diodes were exposed to a lot of heat during soldering. Not a problem, right? I did verify they were both still working after the extensions were complete.

Thanks a lot for your help!

[kyleservicetech]

Originally Posted by GooberRC

OK Dennis - I'm ready to be graded The first pic shows the diode orientation before heat-shrink, and the second shows the entire setup. Lots of cable to tuck away inside the airframe but that's ok. I decided to go with the modified extensions instead of performing surgery on the ESC and UBEC.

I do have one question - the UBEC has a signal wire coming from it in addition to the +/-. I'm assuming that is for programming access and will be inactive in flight. Should I disconnect the signal wire from the UBEC diode extension just in case?

Oh - one other thing: The diodes were exposed to a lot of heat during soldering. Not a problem, right? I did verify they were both still working after the extensions were complete.

Thanks a lot for your help!

Hey!
Excellent job on your assembly.

Your likely correct, that signal wire from the uBEC is only for programming its output voltage. As for me, I'd disconnect it, but leave all three wires in the connector going to the receiver. Makes it a little more secure against coming loose.

As for soldering these diodes, you should see these semiconductors when they go through an automatic wave soldering machine. This is where a "wave" of molten solder flows against the bottom of the circuit board for a full 10 seconds or so. The components on top literally smoke off the flux thats put on the board before soldering.

Before retiring, it was common to see a diode still work OK after being severely overloaded to the point of charring the circuit board.

[GooberRC]

Excellent - thanks Dennis. Now on to the plane itself

[GooberRC]

Got it all hooked up tonight and it worked great. It was pretty cool to be able to pull either one of the voltage sources and everything still worked just fine

BTW - is there an advantage to boosting the default BEC voltage of 5.1V? The UBEC output measured 5.11V both before and after the diode. I thought the diode would cause a voltage drop, or is that only apparent under load?

[JetPlaneFlyer]

Originally Posted by GooberRC

BTW - is there an advantage to boosting the default BEC voltage of 5.1V?

Yes, very much so. Providing your servos are good for 6 volts (most are) then boosting the voltage to 6v increases speed and torque quite significantly. It also gives a more margin for voltage sag before anything bad happens.

[GooberRC]

Originally Posted by JetPlaneFlyer

Yes, very much so. Providing your servos are good for 6 volts (most are) then boosting the voltage to 6v increases speed and torque quite significantly. It also gives a more margin for voltage sag before anything bad happens.

Ah yes, of course. Thanks!

[kyleservicetech]

Originally Posted by GooberRC

Got it all hooked up tonight and it worked great. It was pretty cool to be able to pull either one of the voltage sources and everything still worked just fine

BTW - is there an advantage to boosting the default BEC voltage of 5.1V? The UBEC output measured 5.11V both before and after the diode. I thought the diode would cause a voltage drop, or is that only apparent under load?

Yeah, these shottky diodes have a very low forward voltage drop. Take a look at the curves for this particular diode.

Note the curve goes up to 100 Amps!

[GooberRC]

Thanks Dennis. Only a .3v drop at 5A. Shouldn't be anything to worry about. I'm thinking I'll set both BECs to 6.0V. Sound about right? All my servos and receiver are rated for 4.8-6.0V.

[kyleservicetech]

Originally Posted by GooberRC

Thanks Dennis. Only a .3v drop at 5A. Shouldn't be anything to worry about. I'm thinking I'll set both BECs to 6.0V. Sound about right? All my servos and receiver are rated for 4.8-6.0V.

Yup that should do it.

(For those that want bigger diodes, check this one out! It weighs 6 1/2 Pounds.
http://www.pwrx.com/pwrx/docs/RDS8__80.pdf)

[GooberRC]

Originally Posted by kyleservicetech

Yup that should do it.

(For those that want bigger diodes, check this one out! It weighs 6 1/2 Pounds.
http://www.pwrx.com/pwrx/docs/RDS8__80.pdf)

Thanks. (8000 Amperes would probably cover most applications )