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Sep 06, 2015, 07:20 PM
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Planning for brushed to brushless conversions with SAFE RX/ESC bricks


My first two purchased planes were a Delta Ray and a Sport Cub S; both of which have brushed motors. Because the SCS replacement motors have a reported trend of being very inconsistent as to lifespan I want to start planning for a conversion to brushless. The DR motors may last longer but eventually they will also lose thrust and wear out.

Ideally, I'd like to skip using a PWM to PPM converter and use an ESC that will take a PWM input to run the brushless motor. BLHeli is an ESC firmware that has PWM input as an option. I'm also wondering if SimonK or other firmwares might be alternatives.

Delta Ray planning

NOTE: Brushless Delta Ray project using modified stock brick is completed.

On the Delta Ray I would like to go to an ESC and motor that can handle 3S or 2S power with out blowing out the 2S brick. I am hoping a separate 2S receiver battery for RX and servos and PWM output might work if I wire 3S power for the motors and their external ESCs separately. Alternately, in the resource link it was found the brick can be upgraded to 3S with a capacitor change but that is likely to be too much for small brushed motors.

The correct PWM signal output point appears to be the gate pin on the power mosfet. For the Delta Ray the Gate on each motor FET is pin 4 and output from the MCU coming to the gate is 3v (so a high end ESC or signal amplifier may be needed to handle the low voltage).

I have 2S1500s and 3S 1000s (plus some small 1S and 2S batteries that aren't relevant to DR planning). There are batteries reported on RCG up to 3S1800s that fit without foam mods.

This video (not mine) shows even a small motor can run acceptably with 2S. Parts used in the video are listed in the end credits. I'd like to use something a notch up on power from those used here without adding very much weight.

HobbyZone Delta Ray with little brushless motors (2 min 2 sec)


Resource links:
Problems with converters and DR electronics
https://www.rcgroups.com/forums/show....php?t=2240427

Alternatives (as of Jan 2016 following several months of study and discussion with RCG friends)

1. Keep DR RX/ESC/gyro or flight control "brick" - there are a lot of great features built into the board, including (receiver, 2 motor speed controls with coordination of both motors, SAFE gyro and mixing with self-leveling and panic features, rudder via differential thrust, etc.

a. Replace brushed motors with OEM motors - it works.

b. Replace OEM with Pro180 motors (not recommended without other changes) - Several people have blown a mosfet on the DR ESC. The motors draw more current (see prop tests in my blog) and as Imboeschi has explained in the DR thread the electronics cannot handle this at mid-throttle positions.

b. Amplify the throttle signal coming into the mosfet gates (see Imboeschi's posts in the DR thread, he has done it a couple different ways) and replace the motors.

b. Tap throttle signal from MCU and use external ESC (theoretical at this point?)

c. Use PPM converters (tested by a friend; it worked with signal calibration problems, he later lost the plane)

d. Use ESC that will do the conversion (e.g. BLHeli however this will require electronic and coding knowledge).


2. Add a 2nd receiver and external ESCs to power and control the motors. This means the rudder/differential thrust control is lost unless replaced using an option described below. There seems to be enough room and the weight of a small receiver would be negligible. A number of wiring and electrical options would need to be considered with respect to powering the existing brick and servos but this should be fairly straight-forward. I am not aware of anyone who has attempted this approach with the DR yet, so it is currently theoretical. As mentioned in a comment below, I did a limited test for the SCS that looks promising.

3. Replace DR RX/ESC - this means the in-built features of the DR brick have to be replaced or skipped. Start with a receiver and ESCs - This works with no rudder or SAFE features and you can pick the power level and type of motors, including brushless. Motors can be run without rudder/differential thrust, Elevon mixing needs to be done in the TX or through an add-on feature. Control variations include:

- ESCs on 1 channel with a Y cable (use just 1 BEC power connection)
- ESCs on 2 channels (use TX mixing or possibly add external electronic mixer and consider failsafe needs/issues)
- Aileron and elevator channels using external elevon mixer (if not using TX for mixing)
- Rudder servo and rudder added behind vertical stabilizer

3. Add a gyro for AS3X and self-leveling/panic features to the receiver and ESCs. A number of fixed wing gyros/flight controllers are available but all of them have a large to VERY large learning curve to install. Some appear to include all of the control and SAFE features while some either omit features or rely on a programmable transmitter to handle others.


UM Sport Cub S planning

On the SCS weight is much more critical so my plan will depend on importance and weight of heavier quality battery needed as well as ESC and motor weight.

I could decide to go from 1S brick to a 2S ESC and motor (the Carbon Cub motor has been used successfully. Hoping to use only an ESC to do the brushed to brushless signal conversion and also to control the motor. In addition to the throttle signal conversion, a diode would be needed to step the power down to 1S for the brick.

As a first step in exploring how to do this I found this video that demonstrates how to connect the new ESC to the oem RX/ESC brick (2S to 2S).

1:1MIG15 - How to add an external ESC to your MIG (47 min 0 sec)


The post at the link below has some diagrams and info on a diode to use for stepping power down from 2S to 1S for the SCS brick.

https://www.rcgroups.com/forums/show...09&postcount=2



Here is a pic of the SCS brick where the brushed motor plugs in.


Discussion on the picture above can be found here:
https://www.rcgroups.com/forums/show...&postcount=671

Hopefully the 3rd pin will allow for connecting the external ESC here, but unfortunately the AR6410 manual describes the extra pin on the brushless brick to be "open" (To be determined).
http://www.spektrumrc.com/ProdInfo/F...410-Manual.pdf

Parts
1. Carbon Cub motor with firewall?
http://www.horizonhobby.com/bl180-br...kv-eflum180bl2

Alternatives?
1S alternatives and battery impact?


I have a couple unused 2S motors (1404N and AD100L) but will have to check the specs for amps and thrust for a 5030 to see if either would work with a lightweight ESC instead of buying the EFlite motor.

2. Mount (will UMX Yak mount work?)

3. BHeli ESC with 5v BEC (+step down power with diode)

Option 1 HK ESC & programmer (6A reported to be OK with CC motor)

https://www.hobbyking.com/hobbyking/s...OPTO_2_3S.html

https://www.hobbyking.com/hobbyking/s...istar_ESC.html

4. Diode

5. 2S batteries. I already have these from another UM plane.

6. 2S charger. I already have a couple from other planes.

Status as of 14 Dec 2015
It's not finalized. Read below for other alternative, in addition to what's missing at this date.

BLHeli tests: I'm missing 2 things before I can proceed.

1st - I haven't yet acquired a small 2S ESC that is known to be compatible with BLHeli. I've held off on this since my original motor is still working OK. ESCs with BLHeli firmware loaded are available, but there may still be some electrical and programming issues.

With BLHeli, a programming tool is used to flash and/or change parameters (normally it is set up for brushless input - which I think is the same as receiver PWM. I've gotten the tool and parts to make a flashing jig, however.

2nd - I've not seen a scope reading for the SCS brick, so I don't even know if BLHeli will be compatible. I'm still hopeful because of Crash Override's 1S use of PPM adapters though it may be that the throttle signal needs to be inverted based on his need to reverse the throttle. (Based on a scope picture someone else did for the Delta Ray, that SAFE brick was not compatible without code changes.) Another electrical issue may be the need to match the voltage from the motor leads with a shunt to within an acceptable range for the ESC (or code changes if hardware does not limit).

Alternatives -

A. Dacaur recently suggested using a 2nd 2.7g RX (Orange 415, IIRC) to feed signal to a small external ESC. I think this is likely to work if the Orange DSMX co-binds with the SCS brick. The extra weight is a reasonably small penalty, even if it is not as elegant as a BLHeli direct feed. I suspect there is room for the 2nd RX and ESC, but that will also need to be confirmed. This seems like the next best alternative, and immediately doable if it tests out OK.

B. Use PPM converter and external ESC as per Crash Overrides blog. I don't know if swapping the positive and negative would solve his need to reverse the throttle switch, or if it might blow things up, or just not work.
Last edited by GottaZoom; Jul 27, 2016 at 11:47 AM.
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Sep 07, 2015, 09:10 AM
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RickC_RCAV8R's Avatar
Zoom :

Thanx for posting the schematic . This one grabbed my attention . I was unaware that the linear servos ran on a lower voltage than the standard 5 volts . I inherited a few of these from a heli pilot friend and was getting ready to use them without the 1N4000 series voltage dropping diode in the power lead . You may have saved my servos ! You are my latest hero .
Latest blog entry: Filament Fridge ?
Sep 07, 2015, 09:41 AM
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Well, I'm glad you posted as I learned something! The EFlite spec for the servos is 1S rated. Truth be told I wasn't sure what the linear servo rating was ... I just knew the SCS RX brick was 1S and do not want to risk blowing out such an expensive board.

http://www.e-fliterc.com/Products/De...dID=SPMSH2040L
Sep 29, 2015, 09:08 AM
Registered User
Hi Zoom!

Just tagging your blog so I get notified when you update it.
Sep 29, 2015, 11:31 AM
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Quote:
Originally Posted by AJ.K
Hi Zoom!

Just tagging your blog so I get notified when you update it.
So far I've only been editing the original post. I don't know if that will flag a notification. I will use posts to reference new work by others when it is posted elsewhere, so those posts should create a notice.
Oct 15, 2015, 12:28 PM
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All interested in doing similar mods should look at AJ.K.'s blog. His scope readouts show the DR throttle signal running at about 15kHz. It is one of the resource links for the DR in the OP.
Jan 02, 2016, 04:30 PM
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I got a chance to test SCS Alternative A described in my original post above. So far, it appears to be a possibly viable approach. I'd like to have some different gear (DSMX, smaller ESC and motor) to test, but perhaps someone else has better gear to try.

Here's what I used:

TX
- DX4e, set to DSM2 mode using sticks as explained on page 8 of TX manual.

RX 1
- UM Sport Cub with SAFE, completely stock

RX 2
- Lemon DSM2-compatible feather light 6ch RX @ 2.7g
- HK 8A ESC @ 6g
- HK 9g motor
-2S battery

First I forced the TX into DSM2 bind mode.

Next I rebound both RXs at the same time. The brushless motor spun up and I shut everything down to take off the bind plug from the lemon.

Then I turned on the TX and powered up the SCS. Next I powered up the Lemon RX and the motor worked fine as I moved throttle up. Since I didn't pull the SCS motor plug I had both motors spinning with throttle control.

All of this gear is heavier than I want to add to the SCS but the 9g motor is spec'd at 134g with 2S & 6030 so it could pull it all just fine, albeit with a higher stall speed. The gear is intended for a small Flite Test build, but I realized doing this test might be interesting or helpful to some others, too.

My test also follows a test that an RCG friend messaged me, saying he had similar success using the SCS and (I think) a T-28 that I believe uses a 6400 brick. I'd be interested if anyone else wants to replicate SCS dual RX testing to confirm it works OK for them as well.

I've also ordered a 6A BLHeli ESC via slow delivery from the East. It's also heavier than I'd want to put in the SCS, but I can use it on another small FT build, assuming I don't destroy it in testing.
Last edited by GottaZoom; Jan 06, 2016 at 12:38 PM.
Jan 26, 2016, 08:48 PM
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BLHeli calibration issue post

https://www.rcgroups.com/forums/show...7#post33833242
Feb 16, 2016, 10:12 AM
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Example using a WLToys 1S board

https://www.rcgroups.com/forums/show...postcount=2157
Mar 13, 2016, 03:06 PM
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Amazing - both of these planes had posts today where BLHeli will allow for using brushless motors with the original receiver.

Delta Ray

https://www.rcgroups.com/forums/show...postcount=6643

Which leads to this:

https://www.rcgroups.com/forums/show....php?t=2623782

Sport Cub S

https://www.rcgroups.com/forums/show...&postcount=744

Which leads to this:

https://www.rcgroups.com/forums/show...4#post34245202
Mar 13, 2016, 07:10 PM
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yes, blheli does do that... the trick is getting it flashed onto your chosen esc... there are more and more available pre-flashed these days though, which takes a lot of the aggravation out of it.
Mar 13, 2016, 07:27 PM
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Quote:
Originally Posted by dacaur
yes, blheli does do that... the trick is getting it flashed onto your chosen esc... there are more and more available pre-flashed these days though, which takes a lot of the aggravation out of it.
Yes, following the BLHeli thread and my own buying experience suggests one should be careful.

Some of the pre-flashed don't have the BLHeli bootloader and sometimes the firmware is modified or crippled. Or the ESC may have caps that prevent updates.

So it may be best to use known models unless not being able to make changes is not critical.
Mar 29, 2016, 04:46 PM
Registered User
Hi
I have just bought a DR second hand, immaculate condition.
I will fly it as is while I come up with a brushless motor system.
I can see me going down one of 2 routes
1: the brushed to brushless converter I have found some in America and can import them for this method.
2: second RX with some clever mixing on the TX.

For both I will try with the original LiPo then alter if needed, keeping to 2s will make things easier just have to find a voltage out pad on the DR's board that will not fry any extra electronics. I'll use a combination of a micro BEC free ESC with a motor Commonly found in mini quads.
The first would most definitely be the simplist to make just remove the motors make new mounts wire up the motors to the main board with the converter and ESC between the two. This may not be as easy as it sounds as the converter is an unknown variable, I like the idea of a second RX better though I will be a bit heavier.
Although this is a spectrum based system and I fly with a taranis TX I can fly spectrum with the external module I have, the way I would achieve throttle control and diferentional throttle control at that would be by using both the internal and external transmitter module internal being frsky default inside the TX and the external module being spectrum bound to the DR safe board.
As the safe board has no affect on rudder to my knowledge this should not be a problem. The frsky RX will be controlling the motors only with diferentional thrust provided by the TX the first 6 channels will be standard mainly for the DR's RX safe board channels 7 and 8 will be for each brushless motor, the taranis is fully programmable if you want to do it then all you have to do is work out how to program the TX to do it.
Madden of the stock plane is on Sunday weather permitting, I'll start to design the convertion now.
I have a question does the board have a fear back circuit so it can tell if the motors are there if it does things could be a bit difficult.

Kendrick
Mar 29, 2016, 05:11 PM
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Quote:
Originally Posted by kendrick
I have a question does the board have a fear back circuit so it can tell if the motors are there if it does things could be a bit difficult.
SAFE stabilization activates after the throttle is run up some percentage. (At least the self-leveling portion.) I've always assumed that is based on input from the TX to the DR flight controller (FC). Probably won't know for sure until you test.

Also, the rudder channel input to the FC appears to control the differential thrust to the 2 oem motors. But it may work on both ESCs. Probably will need to test that as well.

Interesting plan. So the Taranis will dual control both radio systems (FRSky and DSM) at the same time? I did know there are two antennas used with some module arrangements. Two DSM2/X receivers might also work but should be tested- reported to work with the Corsair RX but not Apprentice RX in the SAFE in another plane thread.

There may be 5v power on the binding set of pins on the brick (do not use signal pin with ground or it goes into binding mode) - however the maximum amperage out is unknown, which could lead to a brown out on 1 or both receivers if it is overloaded. 2nd receiver may be low draw, but the servos can use a lot with SAFE active.

Safer to just run a small 2nd battery for RX; or wire a single external BEC into wires to the new ESCs. There is an example of the latter elsewhere in my blog.
Mar 29, 2016, 05:52 PM
Registered User
Quote:
Originally Posted by GottaZoom
SAFE stabilization activates after the throttle is run up some percentage. (At least the self-leveling portion.) I've always assumed that is based on input from the TX to the DR flight controller (FC). Probably won't know for sure until you test.

Also, the rudder channel input to the FC appears to control the differential thrust to the 2 oem motors. But it may work on both ESCs. Probably will need to test that as well.

Interesting plan. So the Taranis will dual control both radio systems (FRSky and DSM) at the same time? I did know there are two antennas used with some module arrangements. Two DSM2/X receivers might also work but should be tested- reported to work with the Corsair RX but not Apprentice RX in the SAFE in another plane thread.

There may be 5v power on the binding set of pins on the brick (do not use signal pin with ground or it goes into binding mode) - however the maximum amperage out is unknown, which could lead to a brown out on 1 or both receivers if it is overloaded. 2nd receiver may be low draw, but the servos can use a lot with SAFE active.

Safer to just run a small 2nd battery for RX; or wire a single external BEC into wires to the new ESCs. There is an example of the latter elsewhere in my blog.
My spelling error I mention feedback circuit so the board knows the motor is there and working.
Think you are right on the power front I've ordered a couple of thumbnail size BECs one for the frsky reciver one for the main board if I change cell numbers.
The taranis has one aerial plus a JR module bay at the back that's where the spectrum TX module is put so it will look like it has 2 aerial's.
The main current draw to the board will be from the elevon servos once the motors have been removed, there will still be a signal going to the board on the throttle and rudder channel it just will not have any affect on the motors but it will allow the SAFE system to activate when the throttle is applied at the start of flight.
All motor control will be handed over to the frsky RX on channels 7and 8 mixed there from the throttle and rudder input similar to the way a normal diferentional thrust setup was done in a TX.
Not sure on the motors yet but I think it will be a pair of 1806 2300kv motors one CW one CCW.
Kendrick


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