Savox 1258 brown out
10-25-2012, 11:43 AM
#16
Tech Master
iTrader: (39)
I was racing my 2wd buggy in mod with a 9.5 motor and Tekin RS with a Spektrum SR3100 and an old Hitec 5925 servo. No problems other than driver error.
Then I got a nice deal on a Savox servo so why not install it. Boom, brown outs, couldn't figure out what changed because it's the same everything but the servo. Had it on the bench and low and behold, when giving throttle power and turning the wheels the receiver browned out. AHA, found the problem, the Savox pulls just enough that it goes over the limits of the Tekin's BEC. Adding a receiver cap, a $5 fix, also known as a glitch buster solved the problem and it hasn't been an issue since.
It's not just the servo but everything working together.
Then I got a nice deal on a Savox servo so why not install it. Boom, brown outs, couldn't figure out what changed because it's the same everything but the servo. Had it on the bench and low and behold, when giving throttle power and turning the wheels the receiver browned out. AHA, found the problem, the Savox pulls just enough that it goes over the limits of the Tekin's BEC. Adding a receiver cap, a $5 fix, also known as a glitch buster solved the problem and it hasn't been an issue since.
It's not just the servo but everything working together.
10-25-2012, 12:00 PM
#17
All right, thanks so much for the help everyone! I will give my truck a good look over for any binding issues and then take a look at my steering end points. If it all looks good then I will go and get an external BEC, as the glich buster I have might not be enough.
What is a reasonable trusted external BEC? I know the castle is a classic, just wondering what other options are out there.
One thing that really stumps me is that my Dex410 handles the savox fine with a 60a Ez-run. but hey if it's running fine i'm not going to worry about it.
What is a reasonable trusted external BEC? I know the castle is a classic, just wondering what other options are out there.
One thing that really stumps me is that my Dex410 handles the savox fine with a 60a Ez-run. but hey if it's running fine i'm not going to worry about it.
10-25-2012, 12:18 PM
#18
The highest draw could be from a crash or pipe clip though, so although it's nice information, it's less than ideal. That is unless you never crash or clip a pipe (which is not my case). The volts required are a big gotcha too. My airtronics receiver browns out with .5v swings. So, if I'm running 7v to my servo, and the battery momentarily drops to 6.5v, I get a stall. That happens with each of the servos I've tested (XP, Savox, and Futaba).
Your receiver is not browning out, it is your bec's inability to keep up with the amp draw. The receiver pulls a constant load so that is not the problem unless it is bad.
First if you are trying to run 7 volts to a servo from a 2 cell 7.4 volt lipo that is a problem as a lipos operating voltage is 3.7 volts, if you are running 3 cells the your bec cannot keep up because of your servos high amp draw. and your bec cannot keep up.
Remember this thread is about problems appearing after switching to carpet.
If you have never run on carpet it is much like having or not having power steering, leaving the servo to handle the extra load.
Only trying to answer 1Slash'es ? Carpet is just as hard on the bec as crashes in the dirt. Every input in the steering is double what it is in dirt as to the load on the servo.
Again
(The servo makes up for it by pulling more amps which either results in a BEC Brownout or a voltage drop causing a temporary receiver shut down.)
10-25-2012, 12:41 PM
#19
All right I think I will go and get a castle BEC. What is the correct way to wire one up? I saw this video: https://www.youtube.com/watch?v=zdUhLH7BS4E
And it says you want to remove the middle ESC wire/power wire before plugging it in. Is this correct for my situation?
it makes sense as the ESC would only supplie the motor with power and the BEC would power the receiver and servo.
And it says you want to remove the middle ESC wire/power wire before plugging it in. Is this correct for my situation?
it makes sense as the ESC would only supplie the motor with power and the BEC would power the receiver and servo.
10-25-2012, 01:03 PM
#20
All right I think I will go and get a castle BEC. What is the correct way to wire one up? I saw this video: https://www.youtube.com/watch?v=zdUhLH7BS4E
And it says you want to remove the middle ESC wire/power wire before plugging it in. Is this correct for my situation?
it makes sense as the ESC would only supplie the motor with power and the BEC would power the receiver and servo.
And it says you want to remove the middle ESC wire/power wire before plugging it in. Is this correct for my situation?
it makes sense as the ESC would only supplie the motor with power and the BEC would power the receiver and servo.
Tom
10-25-2012, 01:54 PM
#22
The Spektrum receivers are operating fine, it's just that the BEC is supplying just enough voltage so when the current draw goes up the voltage drops. Both Spektrum DSM2 and Futaba FHSS receivers go into a failsafe mode when it senses a voltage drop below 3.5V.
10-25-2012, 02:08 PM
#23
Tech Master
iTrader: (39)
As far as proof my suggestion is better than your graph, who knows if it was actually connected to your servo or functioning properly( is it set at 12 sec interval or 12 per second?). You say it is. This is something anyone can test for themselves & reading the specs on individual servos can give you a head start. All 3 of those mfg's have servos that they warn you about high amp draw. Sounds like you need a receiver pack.
Your receiver is not browning out, it is your bec's inability to keep up with the amp draw. The receiver pulls a constant load so that is not the problem unless it is bad.
First if you are trying to run 7 volts to a servo from a 2 cell 7.4 volt lipo that is a problem as a lipos operating voltage is 3.7 volts, if you are running 3 cells the your bec cannot keep up because of your servos high amp draw. and your bec cannot keep up.
Remember this thread is about problems appearing after switching to carpet.
If you have never run on carpet it is much like having or not having power steering, leaving the servo to handle the extra load.
Only trying to answer 1Slash'es ? Carpet is just as hard on the bec as crashes in the dirt. Every input in the steering is double what it is in dirt as to the load on the servo.
Again
(The servo makes up for it by pulling more amps which either results in a BEC Brownout or a voltage drop causing a temporary receiver shut down.)
Your receiver is not browning out, it is your bec's inability to keep up with the amp draw. The receiver pulls a constant load so that is not the problem unless it is bad.
First if you are trying to run 7 volts to a servo from a 2 cell 7.4 volt lipo that is a problem as a lipos operating voltage is 3.7 volts, if you are running 3 cells the your bec cannot keep up because of your servos high amp draw. and your bec cannot keep up.
Remember this thread is about problems appearing after switching to carpet.
If you have never run on carpet it is much like having or not having power steering, leaving the servo to handle the extra load.
Only trying to answer 1Slash'es ? Carpet is just as hard on the bec as crashes in the dirt. Every input in the steering is double what it is in dirt as to the load on the servo.
Again
(The servo makes up for it by pulling more amps which either results in a BEC Brownout or a voltage drop causing a temporary receiver shut down.)
The bar chart I linked to is over a period of 12.683 minutes (labeled at the bottom of the chart). I don't recall the sample rate exactly, but it was somewhere around 10 samples/second.
The BEC I was using is a 10amp Castle. It can handle up to 6s input and 10amps. At the time I took the measurement of the graph that I linked to, I was running a 6s LiFe pack and was set output 7v to the receiver/servo. This BEC can handle just about anything that you throw at it, which is why I use it for testing and everyday use. If I were to set this BEC to 10v and used it with a 2s (7.4v) battery, it would basically do 0 regulating. When I do this with a 2S pack, it allows me to find the fluctuations that the receiver cannot handle.
A standard 2S lipo has a nominal voltage of 7.4 as it is 2 cells in series (3.7v x 2). If I were to run 3s (11.1v) as in your example, my BEC would regulate the voltage down to whatever I have it set it (normally 7v on anything >2s) and would have 0 issues with brown outs.
10-25-2012, 02:14 PM
#25
Tech Master
iTrader: (39)
All right I think I will go and get a castle BEC. What is the correct way to wire one up? I saw this video: https://www.youtube.com/watch?v=zdUhLH7BS4E
And it says you want to remove the middle ESC wire/power wire before plugging it in. Is this correct for my situation?
it makes sense as the ESC would only supplie the motor with power and the BEC would power the receiver and servo.
And it says you want to remove the middle ESC wire/power wire before plugging it in. Is this correct for my situation?
it makes sense as the ESC would only supplie the motor with power and the BEC would power the receiver and servo.
10-25-2012, 02:22 PM
#26
All right thanks guys. I will pick one up tomorrow.
10-25-2012, 02:42 PM
#27
Tech Adept
I started out with a rtr slash 4x4, I then added a savox 1258 servo with stock esc and radio and never browned out until I bought a Futaba 4pl radio that's when my brown out issues surfaced.
10-25-2012, 03:13 PM
#28
Based on your response I'm not sure you completely understand the workings of these systems.
The bar chart I linked to is over a period of 12.683 minutes (labeled at the bottom of the chart). I don't recall the sample rate exactly, but it was somewhere around 10 samples/second.
The BEC I was using is a 10amp Castle. It can handle up to 6s input and 10amps. At the time I took the measurement of the graph that I linked to, I was running a 6s LiFe pack and was set output 7v to the receiver/servo. This BEC can handle just about anything that you throw at it, which is why I use it for testing and everyday use. If I were to set this BEC to 10v and used it with a 2s (7.4v) battery, it would basically do 0 regulating. When I do this with a 2S pack, it allows me to find the fluctuations that the receiver cannot handle.
A standard 2S lipo has a nominal voltage of 7.4 as it is 2 cells in series (3.7v x 2). If I were to run 3s (11.1v) as in your example, my BEC would regulate the voltage down to whatever I have it set it (normally 7v on anything >2s) and would have 0 issues with brown outs.
The bar chart I linked to is over a period of 12.683 minutes (labeled at the bottom of the chart). I don't recall the sample rate exactly, but it was somewhere around 10 samples/second.
The BEC I was using is a 10amp Castle. It can handle up to 6s input and 10amps. At the time I took the measurement of the graph that I linked to, I was running a 6s LiFe pack and was set output 7v to the receiver/servo. This BEC can handle just about anything that you throw at it, which is why I use it for testing and everyday use. If I were to set this BEC to 10v and used it with a 2s (7.4v) battery, it would basically do 0 regulating. When I do this with a 2S pack, it allows me to find the fluctuations that the receiver cannot handle.
A standard 2S lipo has a nominal voltage of 7.4 as it is 2 cells in series (3.7v x 2). If I were to run 3s (11.1v) as in your example, my BEC would regulate the voltage down to whatever I have it set it (normally 7v on anything >2s) and would have 0 issues with brown outs.
http://www.rcmart.com/rc-brushless-h...v-p-34566.html
10-25-2012, 04:35 PM
#29
Tech Master
iTrader: (39)
I understand exactly how these systems work, I own a Novak data logger & yes you are right on how an EXTERNAL BEC WORKS!!! That is NOT what we are talking about. We are talking about the INTERNAL BEC's which are normally no more 3 amps & regulate the receiver the receiver voltage to around 6 volts.
http://www.rcmart.com/rc-brushless-h...v-p-34566.html
http://www.rcmart.com/rc-brushless-h...v-p-34566.html
Either way, he says that he's getting an external Castle BEC. So, as long as he leaves the voltage at 6, and the batteries and receiver are capable of supporting the draw, he'll be fine.