Devo 7e + A7105PA + Range mod current draw.

Have just rewired A7105PA module as per PB's latest install guide to measure if TX current draw was any less than the original wiring method when A7105 was not active.

Running recent NB and range modded inbuilt CYRF module with backlight off.

Old wiring / New wiring

100uW - 178mA / 100uW - 112mA
150mW - 199mA / 150mW - 133mA

Looks like my batteries should be lasting longer thanks PB.

Not sure if this is normal but when the A7105PA module is active the range of it's current draw is much less than the CYRF module with either wiring method.

A7105PA active 100uW - 134mA, 150mW - 139mA.

Like some others have reported I also get a humming noise from the buzzer which appears more pronounced at higher TX power settings. When the hum is present the current draw increases by about 60mA and I can measure 1.2 Volts across the buzzer connections.

Moving any trim switch plus or minus can normally stop the hum, the associated current draw and voltage on the buzzer pins. It's like the buzzer is reset to a normal state by the beep produced in response to the trim switch.

It seems that after having to produce a sound i.e turning the controller on, using a trim switch, sometimes the buzzer is not shut off correctly, is this even possible?

Sorry for such a wordy first post and thank you to everybody supporting this project!

that's good info, thanks for sharing

though I am interested in what the different wiring method actually does to the module? and I've seen a couple of people have that buzzing issue with both 7105 and nrf modules when using high output settings but I've never came across it myself.

I have this buzzing issue without having installed any additional modules.
The range mod is not done up to now.
Any other fix than to use the trim every time?

HappyHarry wrote: that's good info, thanks for sharing

though I am interested in what the different wiring method actually does to the module?

If I understand PB's explanation correctly, the new wiring method makes it possible to turn off the A7105 power amp when the module is not active, to prolong TX battery life.

aMax wrote: I have this buzzing issue without having installed any additional modules.
The range mod is not done up to now.
Any other fix than to use the trim every time?

Having read most of other peoples description of "their buzz" there does not appear to be a common set of conditions that cause it to occur. I first noticed it when I had the case open having just done the range mod.
It was after the rewire of the A7105 module and measuring the current draw that I realized that when the buzz was present the current draw was also higher.
My guess is and it is only a guess that the buzz is electrical noise picked up and relayed through the speaker which we hear only because the speaker is "on", when you get the speaker to produce a few beeps in response to a trim switch it seems to then switch "off". I still find that even once it has stopped if you need to use a trim whilst flying the buzz could well start again.

At this time turning the TX volume to zero and relying on vibration only is my best solution!

There is a recent bug report submitted by another user that may have the same root cause.

bitbucket.org/PhracturedBlue/deviation/i...ays-with-high-signal

PhracturedBlue wrote: Fulch:
Can you check the difference in current draw when
1) starting with 'Flysky' and switching to 'DEVO'
2) starting with 'Hubsan' and switching to 'DEVO'
3) powering up in 'DEVO'

The 'low-power' code is not consistent on the A7105, and I'm interested how the different cases compare. I think case (2) should be the lowest power. If so, I will make the other cases behave the same as that.

Results are exactly as you predicted!

All measurements are taken with Sound, Backlight and Vibration turned off.

Case 1: 100uW - 184mA , 150mW - 226mA Checked this one twice to be sure.
Case 2: 100uW - 93mA , 150mW - 139mA
Case 3: 100uW - 98mA , 150mW - 146mA

Also tried Flysky -> Hubsan, Devo -> Hubsan, Power up -> Hubsan, in this case Power up - > Hubsan consumed least but only by 10mA.

With Hubsan protocol I can never measure more than 4mA difference fromm lowest Tx power to highest and have personally flown my X4 at 100uW power out to around 50 feet without losing bind.
Does this imply that the power output scaling of the A7105PA is not optimum when used with Hubsan protocol?

Can anyone, whoes 7e is humming, please verify. (no range mod)

Today i revised all my models and changed the powerrate down to 10mW.
Going down to at least 30mW will stop the noise in my Devo7e.

I think the original Devo7e firmware checked that and so there was no humming before.

BTW, to all who worked on the swithmod: Thank you for this marvelous result.
...3x2 )

I have this humming too, it is on all the modules, cc2500, a7105 and on the stock power modded CYRF.

The humming starts when you increasde output power. It seems not related to RF pickup as playing with the antenna pointing along the board, does not make hum softer or louder.

You can also see the display backlight of devo7e gets a bit of soft flickering when you have the high hum power setting.


I expect there might be a lane, which can't cope with the power or need a bigger capacitor.

I there a schematic of the devo-7e?

The 3v3 supply voltage is clipping can't handle the demand.

At 10mW it is still 3v3 but dropping to 2v8 when at max power.
The small 3v3 regulator, is getting super hot, too hot too touch.

It needs to be replaced by a more capable one.

I switched the buzzer off and turned haptic on. All fine now.
This buzzing was allready there before range mod, it seem to be a 7E thing. My backlight was never flickering.

My measurements from the complett TX is:

The A7105 uses the old wiring but will be changed next time to 6/9
7/8.....while adding the NFR2401.

So these 260mA should be not so hard for the converter.

EDIT:
These 260 mA are max.
Starting in Devo mode it is only 250 mA and what is supprising, when I start with a model with activated telemetry, it draws only 197 mA at 1mW, 206 mA at 10 mW and 233 mA at 150 mW ..???

LCD is from 5 to off = 11mA and from 10 to off 18mA.

What's this new wiring? I am using the basic A7105 without power amp, but my power draw feels pretty bad, my Eneloops (~2100 mAh) barely last 1.5-2 hours before dropping under 5V.

With Deviation 4.01 or earlier, it is advised to bind TXEN to VCC and RXEN to GND.
Works well, but when you use DEVO protocol, it seem that the board will not be put completely to sleep ...( or standby, really don`t known)

With the Nightly, it is said to connect TXEN to GIO1 and RXEN to GIO2.
I think, that due to better protocol handling this will save a little
battery power too.

3v3 should stay 3v3, what ever the Tx power setting, that why there is a regulator.

3V3 Regulator seem oscillating going in current/temp limit, the psu voltage swing you indeed hear on the speaker as hum. A bigger Capacitor on powerline indeed humming weakens, but the problem is the small/hot regulator.

I do not know the schematic, or the type nr of regulator used.

AMS1117 doesn't match the pcb, could wire something in?
www.dx.com/p/ams1117-3-3v-ccl-components...-295891#.U6nJEo2KCZM

Hrm.. I don't have TXEN and RXEN on my module.. it's this one: www.ebay.com/itm/AMIC-A7105-Wireless-RF-...K-GFSK-/280953247359
I presume those pins are part of the power amp then, which I don't have.

Output currend up to 1A. That should be enough

www.advanced-monolithic.com/pdf/ds1117.pdf

@Arakon
Sorry, this might be good for Arduino projects, but not for RC planes/copters.
Range too low.You better take a modul of a V911_TX or buy something like
the A7105 DO3 modul.

www.banggood.com/XL7105-D03-A7105-Modifi...Flysky-p-922603.html ( no antenna)

I use this.
www.banggood.com/A7105-Wireless-RF-2_4GH...Module-p-909404.html

Looks the same but who knows.

But the 1117, dropout voltage is 1.1V so it means, 4x NI MH battery must be above 4.4V. But 4.4V can be considered as empty.

I'll order the module from BG

It is even good for you cells not dropping the voltage to much.
With my NiMH cells i stop at 4.4V alarm.

aMax wrote: @Arakon
Sorry, this might be good for Arduino projects, but not for RC planes/copters.
Range too low.

I use it only for the Hubsan X4, and that is so small that it's out of (usable) sight before it gets out of range even with the basic module.
I've flown it outdoors within usable distance and usually just fly it indoors.