Jump to content
provdes

LED lights flickering when servo is used

Recommended Posts

I have purchased some LED lights to use for a beetle-rod style buggy project and one of the lights is an LED array I am going to mount on a roof rack.

It's an all-new electrical set up and when I tested it all, the LED array lights up (but way dimmer than I expected) and works on Ch3 and I can switch it on and off and cycle between the different modes it has, but when I operate the servo the light flickers and dims. I was also expecting the light to be way brighter (it has 32 LEDs in it!).

It looks like there is not enough juice being supplied to the light. Do I need to change something in my setup?

This is what I currently have:

Dollatek ESC - 60a (2-3 lipo BEC: 5v/2a)
Savox SC-0254 digital servo
2s Lipo battery 4200mAh 50c 7.4v
The LED light is one of these from Amazon, and there is little info on it other than it is 5V-8.4V
Absima 4ch transmitter and receiver.

I am not an electrics guy and this is my first attempt at fitting lights to an RC.

I am guessing that I might need a beefier ESC, a 3s battery or a separate power supply for the lights... Any recommendations would be greatly appreciated.


 IMG_9191.thumb.jpg.6ae036edcc9c1c6271ae1850b702a87f.jpg

Share this post


Link to post
Share on other sites

The Savox 0254 is a great servo, but in my experience they're quite power hungry.  It's probably drawing enough current to brown out the LEDs.  LEDs typically don't require much current but they are voltage sensitive, so if the servo draw is causing a voltage drop, they might dim or go out.  One solution to this is to fit a power capacitor.  This plugs into a spare port on your receiver and can smooth out the voltage drops across the electronics.  Also helpful if your radio stops working when you're changing direction quickly (happens a lot with my Orange receivers).  Most RC shops should sell them.

Another alternative, since the LED kit is rated to 8.4v, is to run it direct off the LiPo, using an adapter that goes between the battery plug and the ESC.  Your 2S LiPo should never exceed 8.4V, so that should be safe, but a 3S LiPo will be too much.

Some ESCs have an optional setting for 7.2v BEC output, but check the specs on your radio, if it's not rated to 7.2v it may be damaged (I've run a few cheap radios on 7.2v and never fried one yet).

  • Like 4

Share this post


Link to post
Share on other sites

@Mad Ax Thank you for the info! Makes a lot of sense. Might try the capacitor as its the simplest and cheapest approach. I've seen a Savox one here.

If my lights are still a bit on the dull side (I think the BEC output on my ESC is max 5v and there is nowhere to adjust it on the programme card) I'll try wiring them into the LiPo. I've seen some harnesses that would get me most of the way there. 

Is it possible to have the switch wire from my lights still go into a jr connector into my receiver so I can turn them on and off with the transmitter? 

Share this post


Link to post
Share on other sites
55 minutes ago, provdes said:

Is it possible to have the switch wire from my lights still go into a jr connector into my receiver so I can turn them on and off with the transmitter? 

Yes, I think this is what @Mad Ax was suggesting.  You can make (or buy) a signal/power splitter, so that the light is getting the signal from the Rx and the power from the LiPo.  These are pretty commonly used with high-voltage servos, but would be an easy solution for full switchable power for your lightbar.

Share this post


Link to post
Share on other sites
2 hours ago, provdes said:

Is it possible to have the switch wire from my lights still go into a jr connector into my receiver so I can turn them on and off with the transmitter? 

Assuming the light system currently has this facility (when plugged directly into the receiver) then yes.  In your photo, I see a white (signal) wire going from the light control board into the receiver plug.  If you're currently able to turn the lights on and off from this channel, then you can do this if the lights are powered by the LiPo.

You'd need to connect the black and red wires from your light unit into the black and red wires from the battery, and the white wire from your light until into the Signal terminal on that channel of the radio.  You can buy kits to make JR plugs if you want to make up a new harness to do this.  This will work as long as you're using the same battery for the ESC/radio and the LED unit.  If you use a totally different battery for the LEDs, you'd need a common ground between everything.

I hope that makes sense :) 

Share this post


Link to post
Share on other sites

This is the cause of your problem. 

9 hours ago, provdes said:

Dollatek ESC - 60a (2-3 lipo BEC: 5v/2a)

Made worse by this. 

9 hours ago, provdes said:

Savox SC-0254 digital servo

That servo will suck up about all the 2A coming out of the ESC and you still need to power the receiver (about 0.3A) and LED. 

Stick a 8A UBEC in and you can power all the lights you want. 

5 hours ago, provdes said:

Is it possible to have the switch wire from my lights still go into a jr connector into my receiver so I can turn them on and off with the transmitter?

I have the same LED as yours and it is very bright. It can be switch via pressing the button on the circuit thing between the plug and LED or by plugging it into CH3 and clicking the button on your receiver, works both ways. With an UBEC, you need not "break" up the connectors on the light and just plug it in normally. 

  • Like 1

Share this post


Link to post
Share on other sites

@bRIBEGuy @Mad Ax @alvinlwh Thanks all for your responses!

I've got the LED working on the Ch3 button on my transmitter so all good, but as you say, woefully too little amperage from the ESC which is all being stolen by the servo.

I was reading about UBECs and thought this might be a solution. It still looks like I might need to do a little wire chopping and soldering to get power into the UBEC but that all looks like part of the fun.

What would the advantages be of a UBEC over wiring the lights directly to the battery? 

Also, have you invested in crimping tools for JR connectors or is it possible to crimp them with pliers?
 

Share this post


Link to post
Share on other sites
8 minutes ago, provdes said:

I was reading about UBECs and thought this might be a solution. It still looks like I might need to do a little wire chopping and soldering to get power into the UBEC but that all looks like part of the fun.

What would the advantages be of a UBEC over wiring the lights directly to the battery? 

UBEC is easy to do. You have two options, make up an adaptor between the battery and ESC with a male and female on each end, and a tap off for the UBEC. The advantage of this method is the UBEC can be transfered between cars. The disadvantage is you need plugs and suitable wires. The other method is to open up the ESC battery connector and solder the UBEC on directly. The advantage is less materials needed and the disadvantage is the UBEC is less easy to transfer between cars. Both methods, it will unswitched so permanently on when the battery is connected. 

As already stated by Mad Ax, your servo is power hungry, a UBEC will power everything, ensuring that not just the LED gets enough power, but the servo too. Get a 5A or more UBEC for sufficient power. Also, it makes wiring the LED simple. 

You may or may not have already came across this problem. 

An UBEC eliminates this problem completely. BTW, I have the same brand radio as you and my problem was blamed to the "cheap" radio by some so called "experts" when it was really a power supply problem. 

17 minutes ago, provdes said:

Also, have you invested in crimping tools for JR connectors or is it possible to crimp them with pliers?

I use the UBEC to ESC battey plug solution, no crimping needed, just a small screwdriver to slide the red cable out of the JR plug. 

 

  • Like 1

Share this post


Link to post
Share on other sites
On 9/12/2022 at 9:53 AM, provdes said:

but when I operate the servo the light flickers and dims

Actually, after thinking over this, your problem is exactly the same as this. 

Instead of it showing up on lights, mine shows up on the motor. Basically the servo sucks so much juice that it caused a low power situation elsewhere. In my case, it is the RX that lost power briefly and it reset as if turning on for the first time. This caused the ESC to think that it is a startup so it turn the motor slightly to make the beep sound. If it happen many times in a very short period of time, it looks like the motor is turning (it should not turn but just twitch). 

I had tried making this capacitors Mad Ax talked about but they did not work, as the ESC supply is too low to start with. My estimate is your set up needs at least 3A even without the lights, 2.3A for the servo, 0.3A for the RX, 0.3A for the fan on your ESC. If the Savox is as power-hungry as they say, then it may need 3.5A. No amount of capacitor can compensate for that much difference in power. I even made a unit that is 4 times the capacity of commercially available ones, still no joy. 

So in your case, I really suggest getting an UBEC. 

  • Like 1

Share this post


Link to post
Share on other sites

@alvinlwh Thanks for all the info and links!

I was thinking about just getting another ESC with a better built in BEC to keep things clean inside (I'll be fitting it all inside a 1/10 2WD buggy so space is limited) but I think I've found a nice compact 8A UBEC and the required harnesses to do it all without any crimping or soldering, so I should be able to solve it all for under £20.

I might upgrade to a more powerful ESC when I do my next kit.

I'll post some photos here when I'm done :D

  • Like 1

Share this post


Link to post
Share on other sites
3 minutes ago, provdes said:

I've found a nice compact 8A UBEC and the required harnesses to do it all without any crimping or soldering

I think you may have bought the same set as me as my 8A came with the harness as well. 

One thing you may want to get, if you do not already have it, is a servo tester. You can then know exactly how many A your servo draws to help with your BEC calculation. A rough guide is 1A per 2 - 3kg. Some ESC program cards already have this function so you may already have one? 

Share this post


Link to post
Share on other sites
5 hours ago, alvinlwh said:

One thing you may want to get, if you do not already have it, is a servo tester. You can then know exactly how many A your servo draws to help with your BEC calculation. A rough guide is 1A per 2 - 3kg. Some ESC program cards already have this function so you may already have one? 

The UBEC I have coming only has 5V / 6V switch for the output. It puts out a consistent 8A or 15A burst (it is this model) so I don't have many options on the calculations. I was just going to try it on 5V and see if it works well. If not, switch it up to 6V!

Share this post


Link to post
Share on other sites
2 minutes ago, provdes said:

The UBEC I have coming only has 5V / 6V switch for the output. It puts out a consistent 8A or 15A burst (it is this model) so I don't have many options on the calculations. I was just going to try it on 5V and see if it works well. If not, switch it up to 6V!

I just set mine at 6V. Most modern servo can handle that and performs faster at 6V. Mine can even go to 7.4V for HV servos as well. I like that yours has a switch, time to look for one.

Share this post


Link to post
Share on other sites

@alvinlwh After having to wait a little while for some parts to arrive, then a little soldering to change a connector on the UBEC, I now have everything working! Thank you and @Mad Ax and @bRIBEGuy for your help :D

With this set up the lights are now at full brightness (soooo bright!), nothing flickers when I use the servo, and I can be happy in the knowledge that enough juice is getting to my servo. The big LED works nicely on the channel 3 switch on my transmitter and I can cycle through the lighting modes. The other lights don't have a switch wire so I may add a switch to them - I would like to get a rear set of red LEDs to add to this.

Next challenge will be finding space for all the wiring in my skinny 2WD buggy chassis. Downside to harnesses is the bulky extra connectors and excess wire everywhere. Zip ties to the ready!
 

614972506_RCCARUBECBYPASSWIRING2SLIPO.thumb.jpg.608033dba4d69245c832d1d67221b35b.jpg

  • Like 3

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

×
×
  • Create New...