Using 7.4v servo - power supply options?
 

I'm considering the purchase of a servo that accepts 7.4V of power.

What I'm wondering is how I should power it?

I'm going to be running a Spektrum SR200 receiver and a 2S lipo.



I've found a UBEC with 7.2v out at 4.5a



would this damage anything if I powered my RX with this high of voltage?

Or should I run that UBEC directly to the the +/- wires coming from the servo?
But if I do this, I might as well just power the servo right off my balance lead, right? Or does having this provide any advtange? I guess it would give me the capability to use a 3S later if desired?

Any answers are greatly appreciated! Thanks!

7.4 power
 

I'm running several of my SC trucks direct. I got a bag of the Align magnets and run the wire I hook up to the + & - on my ESC thru the magnet 3 or 4 times to filter the interference out and the plug it in the battery slot in the rec. Works much better then any cap will. I then pull the positive wire out of the ESC receiver plug so the ESC is isolatted from the power for the servo and Rx

Most guys add lead, I added a separate small (350mah) lipo just for the receiver/servo. I never have to worry about any noise or brown-outs etc...

So I've got one vote for direct from batt, another vote for separate battery.

I feel like there isn't a reason not to use a BEC, correct me if I'm wrong?


From my understanding:
The reason why one might see noise/interference is because of voltage fluctuation?

Brown-outs may occur because of either voltage drops or BEC failures?



Btrukr, you're saying you have something like this? (add the dots)

i imgur com/1fzI6 png

filter
 

The first and every BEC after that have the same filter on the rec lead. Most aircraft esc's use this style of ferret magnet to filter the power. The first time I did it, I tried a cap to catch the surge from the source when you hit the brakes or accel hard. Without a filter on the esc powering the rec, the car turns right or left from the surge. The little magnets are like 3 for 2.50 at my local hobby store, so I went this way because it was cheap. You can buy a 5A/6V bec for $5-10 and they really protect the esc. I have been using the Solar D770 servo in my buggy(.06@148/7.4). I thought for 15 I'd just replace it if busted, but I have an extra and I've not used it.

I use the castle 10amp BEC, Its 21-25 bucks, and it works great. I use it on all my Monster trucks. Never have had a issue. Its much lighter than installing a extra battery.

I looked at this one and considered it, did you have to buy a USB adapter to get the settings right for it?

Anyways, I ordered a hobbypartz 7.2v 4.5a ubec. If it doesn't work well I can always drop the extra coin for the castle one.

Thanks everyone for the info!

That was the option of hooking up the battery directly to power the rx, which I guess isn't good because of voltage fluctuations under power and braking, I've decided to go with a BEC

direct
 

Sorry I didn't mean it would surge if you use a filter. The battery powering your car is easily powerful enough to spare 3-5 amps to run the rx and servo. I use the castle bec on monster trucks and my truggy.

The castle BEC comes preset at 5.1 volts. I set mine to 6.0 since I dont have HV servos. Yes you need the usb connector to program at a different voltage. I have the field card which is very nice. I can program the speedo's in the field without the need of a computer, and hook up to the computer and run the computer software threw the card. The BEC will need to be programmed from the computer. Its the same software interface as the speedo's. Im sure someone you know has castle stuff, or the LHS can do it. Most of them around me will help people out and program their stuff for free.

Seems like a very well done BEC, only time will tell to see if I need one.

Sorry what's the reason why you can't use the bec built in the esc? And just run the red wire of the servo directly to the + side of the pack?

Correct me if I'm wrong, but it's most likely because of voltage sag. When a car undergoes hard acceleration or braking, the battery will be under a load it may not be able to keep up with fully, thus the voltage potential on the battery drops temporarily. Because of these voltage differences, this may harm a servo or cause erratic behavior. And BEC's are cheaper than having to buy another servo, even if it is only $15