SL-8 Recevier and Graupner Speed Profi 40 r Question

[Teaker11]

After talking to Airtronics, I have scrapped the Airtronics and buoght An SL-8 recevier and 8 channel Wfly transmiter. My question is I am building Engal German MK VIIc Sub and I have bought 2 Graupner Speed Profi 40r Speed controllers.
I am running the boat on 12v Batteries. My question is will I be able to run 2 controllers one for each prop. with the BEC and not have any problems. I would like too use both sticks for the motors. Will that set up work with the SL-8? I will not receive the transmitter and recevier till Wed. and I do not want to damage the recevier.
any help would be wonderful
Thanks
Jim

[sombra]

You can only use ONE BEC to power the SL-8. The BEC of the other controller should be turned-off.

[Albion]

A boat of that size i would run a separate BEC

[Teaker11]

How would you shut off the BEC, or run a seperat BEC ?







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[Subculture]

Usually you remove the red wire from the servo lead. Some ESC's provide a jumper for this, which makes life simple, but most don't.

An independent BEC is simply run from the main battery pack to a spare channel on your receiver. If you don't have a spare channel , then use a y-lead splitter to share the channel.

[Teaker11]

Ok thanks for the advice. there are alot of circuit boards on this boat and a seperate line from the main battery's might be the answer, but it is a 12 volt system..

[Subculture]

Don't run 12 volts directly to your receiver, you'll cook it. You can get dedicated BEC's capable of delivering 3-5A. Most ESC BEC's can supply 1-1.5A maximum at 5 volts (about 5-7.5 watts), which is marginal for a sub with three servos plus the piston tank control boards, but I'd be inclined to try it and see- worse case scenario is that you have to disconnect it.

Most servos draw an average of about 1 watt in operation, they can draw considerably more than that if stalled, so make every effort to ensure the linkages don't bind up in any way. With three servos, that's 3 watts. Items like levellers and ESC's draw relatively little current from the receiver, so I would worry about them. The piston tank controller may draw another watt or so as it uses relays. It's unlikely you will be using all channels all at the same time, so assuming you have a maximum of 5 watts output, the built in BEC should just about be adequate.

[Teaker11]

Yes I know not to rune the recvier with the 12 volts, I was just thining that with the amount of batteries It would be better, I will use the BEC off of one of the motor controller and cut the red out of the other Speed Profi 40R. I spoke with Graupner and they said it should work, but they recomended the Navy version in place of the ones that I have. I bought these off of Engal's Site so we shall see in a couple of days.
Thanks all for the help
Jim

[Subculture]

Generally you only need between 0.5-2.5 volts (depending on the regulator chip used) above the voltage you wish to regulate e.g. 5.5-7.5v for a 5v output, anything above that is just shunted to ground and burnt off in heat. So although you need sufficient voltage for the BEC to work, going too high is not good either, and your BEC will supply less current at 12 volts than it can say at 7.2 volts.

It would be possible to use both BEC's if you split the power bus to your servos, say run half the servos off one BEC, and the others on the other BEC, but this would involve modification of the servo leads, so it's easier to just use the one.

[sombra]

Generally you only need between 0.5-2.5 volts (depending on the regulator chip used) above the voltage you wish to regulate e.g. 5.5-7.5v for a 5v output, anything above that is just shunted to ground and burnt off in heat. So although you need sufficient voltage for the BEC to work, going too high is not good either, and your BEC will supply less current at 12 volts than it can say at 7.2 volts.

It would be possible to use both BEC's if you split the power bus to your servos, say run half the servos off one BEC, and the others on the other BEC, but this would involve modification of the servo leads, so it's easier to just use the one.

True if your BEC is using a linear regulator. However, a lot of manufacturers use switching regulator for BECs that offer very high efficiency, so you don't waste your batteries heating up your model.

[Subculture]

It's not usual to to find a switchmode BEC in a brushed ESC, and they're certainly not fitted in the Graupner units mentioned here. They tend to be fitted into controllers aimed at flyers and usually for higher voltage brushless operation. You can get stand alone switched mode BEC's quite inexpensively, and I've seen them used very effectively.

There was some discussion on another forum about the noise generated by switchmode BEC's and it's subsequent negative effect on radio reception, which is already pushed in a sub aquatic environment.