Electronics questions

[baker3]

Ok guys so I am getting ready to build up the large bruder dozer and am looking to see what type of electronics I need to look at to run the servos and what not. I want to use 2 firgelli rams for the blade and one for the ripper. Do i need to use ESC's or would I just run the receiver straight off a battery?

[Lil Giants]

Assuming you're using modified 360 servos to drive the dozer? the firgelli actuators have their own esc built in, then probably all that's needed is a BEC from Castle Creations to power everything through the rx. Then you're not limited to using just the rx 4.8v batt, but rather 6,7,10 cell or 1,2,3,4,ect lipo of any amp size.

http://store.rc4wd.com/Castle-Creati...or_p_2253.html

http://store.rc4wd.com/Castle-Creati...or_p_3536.html

2nd one is programmable to set limits for voltage & amperage outputs via your computer with this device.
http://store.rc4wd.com/Castle-Creati...t-_p_1348.html

[baker3]

Yes, I will mod the servos to run continuous. Thank you for all the info!! I really appreciate it!

[baker3]

Ok gents, I need some help. I just got my large sail winch servos and they were supposed to be a 360 continuous rotation. I took the gear cover off and removed the gear that sits on the output shaft and then it would rotate non-stop, but as soon as I re-install that gear it only turns a few times. Anyone have experience with this servo?

[baker3]

here are some photos.

[RCP57]

I don't have any personal experience with them but don't they typically only turn 3.5 times or 1260 degrees without modification?

[baker3]

Ok oztruck, so I tested the servo on a RC crawler ESC I have laying around and wired the servo motor directly to the ESC. I was able to get it to continuously rotate but when I put it into reverse, one of the little flat black boxes heated up and glowed orange on the servo controller. Here is yet another question. The ESC I have runs 2 motors. Is there a way to know whether the ESC will be able to operate the servos independently or will I have to buy a certain type of ESC? I only have a gun style controller to test on now until my turnigy gets here.

[Espeefan]

Glowing orange IC chip? That's not good! At this point you might be better off simply removing all of the electronics inside the servo, and hardwiring the servo's motor leads to a separate ESC, as you did for testing.

If you want to run two motors individually, you will need two separate ESCs, each running on it's own radio channel, or else one ESC designed to run two motors individually, on two separate channels. Dimension Engineering's Sabertooth line of ESCs would be great for this. Even if all you have is a simple 2 channel pistol grip style radio transmitter.

http://www.dimensionengineering.com

[baker3]

Thanks for all the info!!! Ya, I pretty much decided that I will run the 2 servos off a separate ESC...I been eyeballing that sabertooth ESC for a while but want to see if there are any cheaper options out there. I want to build this as cheap as possible but if there are no cheaper better alternatives, I will bite the bullet on the sabertooth. Any suggestions?

[Espeefan]

Baker3, I think independent dual motor ESCs are generally not cheap. You could also run two separate single motor ESCs as well. A radio transmitter with dual sticks would be ideal for running a set-up like that. Single motor ESCs can be found for very cheap, but the catch is you need two. If you can keep the cost under that of the Sabertooth 2x5 ESC, which is $60, it would be beneficial. Otherwise, you might just be better off with a Sabertooth.

Perhaps someone knows of a cheaper dual motor ESC. I would suggest checking with some robot supply stores for something really light duty. The servos shouldn't pull much more then 5 amps. You might try posting a wanted for something second hand.

On another note, it is possible to convert normal servos into continuous rotation servos quite easily. The internal circuit board of any servo makes a great built in ESC, once you've made the conversion. Then no external ESC is required at all. Each servo would have it's own.

[baker3]

Originally Posted by Espeefan

Baker3, I think independent dual motor ESCs are generally not cheap. You could also run two separate single motor ESCs as well. A radio transmitter with dual sticks would be ideal for running a set-up like that. Single motor ESCs can be found for very cheap, but the catch is you need two. If you can keep the cost under that of the Sabertooth 2x5 ESC, which is $60, it would be beneficial. Otherwise, you might just be better off with a Sabertooth.

Perhaps someone knows of a cheaper dual motor ESC. I would suggest checking with some robot supply stores for something really light duty. The servos shouldn't pull much more then 5 amps. You might try posting a wanted for something second hand.

On another note, it is possible to convert normal servos into continuous rotation servos quite easily. The internal circuit board of any servo makes a great built in ESC, once you've made the conversion. Then no external ESC is required at all. Each servo would have it's own.

Hmmm the sabertooth I looked at was $140...I am obviously looking at something way too high powered for this application lol...total noob at this...I am trying to keep it low budget because a few of my buddies are interested in doing this as well. I was the test dummie. $60 is not bad.

Oztruck, do you have experience with that ESC? Also, I would need to run 2 right?

[Espeefan]

Originally Posted by baker3

Hmmm the sabertooth I looked at was $140...I am obviously looking at something way too high powered for this application lol...total noob at this...I am trying to keep it low budget because a few of my buddies are interested in doing this as well. I was the test dummie. $60 is not bad.

Oztruck, do you have experience with that ESC? Also, I would need to run 2 right?

Wow, yes, you must have been looking at one of the higher current Sabertooth ESCs. The 5 amp model at $60, 'ought to handle those servos. If you wanted to be safe, you could buy the next size up, but I can't really see a servo pulling more then 5 amps, unless it's stalled completely.

[baker3]

So all four would plug into a BEC?

[baker3]

Cool, so the BEC's I been looking into are castle creations...is those good ones to go with?

[Espeefan]

Castle makes great BECs. I've used them for years and have no complaints. Their 10 amp BEC (switching regulator) is what I'd suggest purchasing, if you need it. If you are planning on running all your servos with ESCs, you will not need an external BEC though.

[baker3]

I really do appreciate all the info you guys are providing!!! So where would the battery plug into to power all this stuff? With 4 ESC's plugged into the rx, where does the battery plug into? Im confused cuz my crawler uses 1 ESC to power the rx.

[Espeefan]

Your ESCs would plug into the receiver, however they will not be drawing their power from (or through) the receiver. They will get their voltage from the main battery pack you choose to run the model with. So when you wire up your ESCs, all of them will have to connect to the main battery pack, in parallel. You could do this a few different ways. One way would be to make a Y-harness that splits the battery pack's leads into 2 or more leads, with each lead going to the input wires of each ESC. Another thing you could do is run the battery wires into a terminal strip, and then branch the multiple circuits off that terminal strip to each ESC.

Your ESCs typically supply power to the radio receiver, not draw power from it. BEC stands for battery elimination circuitry, so any ESC with an internal BEC can power your receiver, and you will not need any extra battery packs for that. You can run the model, and all the associated on board electronics, with the main battery pack.

When do you need an external BEC then? When you start to run a lot of high power servos off the receiver. Often times an ESC's internal BEC can only supply 1 to 5 amps of current to anything else plugged into the receiver. A couple high torque servos can easily over tax the internal BEC, causing the ESC to glitch or shut down (thermal) so by running an external BEC, your ESC is free to just run the main drive motor and life is good.

When I mentioned you might not need an external BEC, I assumed if all your servos are going to be driven by the ESC, you will basically be treating each servo like just a regular drive motor. These servos will not need to be plugged into the receiver at all. Your ESC will be handling the control (speed and direction of rotation) and the voltage they get.

If you think you want to run a couple servos, as true servos, off the receiver to lift a blade or ripper for example, then you might want to think about adding an external BEC for that. These ESCs you are looking at have very weak internal BECs (at just 1 amp).

[baker3]

Thanks man!!! Im a noob to all this DIY RC stuff so barney style instructions are greatly appreciated lol. So for 2 drive motors/servos, the Sabertooth 2x5 R/C would work and for the ripper and and blade servos would be able to use a less expensive one?

[Espeefan]

Yes, you can do exactly that, if you like, though if you want to be on the safe side with current draw on the track drive, maybe think about stepping up to the next biggest Sabertooth ESC, if money permits.

I would also think about using the blade and ripper servos as actual servos, with no ESC running them. Unless you need more travel to raise and lower the attachments. You can always increase the travel/throw of the servo by using a longer servo arm, with the attaching linkage out to the furthest hole, though you'll loose a little leverage (torque). If you run your blade and ripper servos with an ESC, there will be nothing to stop the servos from rotating past or over center, except you the operator, and that may or may not matter. It's something to think about though.

[Lil Giants]

I thought he said he was using Firgelli actuator rams for blade & ripper.