Jumper T8SG - First TX stock running on Deviation

I am experimenting on ways to get my first batch transmitter to run well on 4xAA eneloops, or a single 18650 Li-Ion cell. The combination of Pololu item #2122 and #2564 for the 3.3v and 5v regulators looks very promising. I bought a set of these a week ago at regular price. And now I see that Pololu has a sale going on with a good price drop through Monday 11/27. Wanted to bring attention to the Pololu sale for anyone who has an inclination to experiment. www.pololu.com/blackfriday2017

Any news on the gimbals? I have my money saved

I have experimented replacing the original hi-dropout voltage 3.3v and 5v linear regulators with Pololu up/down 3.3v and up 5v switching regulators on 4xAA Eneloops or 1x18650 Li-Ion battery. The goal was to keep the power shutdown and save circuitry untouched. No problems with the 4xAA in this setup (no surprise since the Walkera 7e circuitry was designed for 4xAA). With the single 18650, the Pololu regulators work well maintaining the 3.3v and 5.0v through the full range of battery voltage 4.2 - 3.0v, and therefore the system operates fine until shutdown. At shutdown the original hardware circuitry succeeds in saving model changes only for battery voltages above 3.8v. Below 3.8v there are no model change updates at shutdown regardless of the batt_critical voltage setting. Looking at the power shutdown circuitry, the 560K - 560K voltage divider at mcu pin A3 seemed to be a likely cause. As battery voltages drop below the design voltage, it is reasonable that A3 will at some point not have enough positive signal to trigger the shutdown save operation. So I reduced the 560K between A3 and J1 switch pin1 to 240K, and the shutdown save now works fine down to 2.8v. With that it seems possible to have a single 48gram Li-Ion cell provide 3000+mah. The reduced weight is nice. Note that 4 Eneloops in a Walkera battery holder are around 125grams.

yets wrote: Any news on the gimbals? I have my money saved

Me too!

Btw allready 305 preorder for Jumper at Banggood by today (and it is sold elsewere)
For the irange transmitter 553 preorder.

That means in few weeks time the user community for deviation grows fastly ?? Can we see it allready in the nr of pageview or downloads ?

@FDR, thank you for keeping this place clean, we don't see spammers at most, and it is because of your efforts.

hear, hear

well I have to say all I have got from here is nothing but good info, I am new to the hobby and without you guys there is no way I would of got this transmitter bound to my micro quads or even got the quads in the air. And it has been fascinating to see the interaction between the developers and Jumper, keep it up...

yets wrote: Any news on the gimbals? I have my money saved

Due to some tooling issue , it can't be mass production now , it will be a little delay ...........

dc59 wrote:

yets wrote: Any news on the gimbals? I have my money saved

Due to some tooling issue , it can't be mass production now , it will be a little delay ...........

Thanks for letting us know. A little delay is no big deal. I would rather have a nice working gimbal than to deal with return issue.

So which hall sensor chip is going to be used? MLX90393, some other digital or analog?

So dear friends ,For 2cells lipo battery (8.4v) what should be the mini power point set up for batt alarm??

dc59 wrote:

yets wrote: Any news on the gimbals? I have my money saved

Due to some tooling issue , it can't be mass production now , it will be a little delay ...........

As long as it's still in production I'm happy to wait! I'd be heartbroken if they turn around and say they can't make them

Thanks...

ramunas wrote: I have experimented replacing the original hi-dropout voltage 3.3v and 5v linear regulators with Pololu up/down 3.3v and up 5v switching regulators on 4xAA Eneloops or 1x18650 Li-Ion battery. The goal was to keep the power shutdown and save circuitry untouched. No problems with the 4xAA in this setup (no surprise since the Walkera 7e circuitry was designed for 4xAA). With the single 18650, the Pololu regulators work well maintaining the 3.3v and 5.0v through the full range of battery voltage 4.2 - 3.0v, and therefore the system operates fine until shutdown. At shutdown the original hardware circuitry succeeds in saving model changes only for battery voltages above 3.8v. Below 3.8v there are no model change updates at shutdown regardless of the batt_critical voltage setting. Looking at the power shutdown circuitry, the 560K - 560K voltage divider at mcu pin A3 seemed to be a likely cause. As battery voltages drop below the design voltage, it is reasonable that A3 will at some point not have enough positive signal to trigger the shutdown save operation. So I reduced the 560K between A3 and J1 switch pin1 to 330K, and the shutdown save now works fine down to 3v. With that it seems possible to have a single 48gram Li-Ion cell provide 3000+mah. The reduced weight is nice. Note that 4 Eneloops in a Walkera battery holder are around 125grams.

Please share more detailed information with pictures when you have time, I would love to mod this TX to use with either 4x AA or 1x 18650. Thank you for experimenting to make this possible.

This is indeed of interest, I had problems I could not switch of anymore the TX at low voltage, can you confirm the battery monitoring still works fine doing this mod? Btw a vbat calibrate parameter scale and offset, would be nice too have too.
I managed to fit two 18650 in parallel in my devo 7e, using single lipo or ion, we can easily charge over USB, as there are many charging circuits avaialble.

Fernandez wrote: This is indeed of interest, I had problems I could not switch of anymore the TX at low voltage, can you confirm the battery monitoring still works fine doing this mod? Btw a vbat calibrate parameter scale and offset, would be nice too have too.
I managed to fit two 18650 in parallel in my devo 7e, using single lipo or ion, we can easily charge over USB, as there are many charging circuits avaialble.

I can confirm that the battery monitoring circuitry actually surprised me in it's accuracy. Actual battery voltages from 4.20v to 3.03v were reported as 4.15v to 2.97v (averaging about .05v -.06v low. But note that my particular Pololu 3.3v regulator is putting out 3.33v (1% high). That will cause the voltage reported to the monitor to be low by 1% or about 0.04v. So the actual error in the circuitry is less than 1%. I agree that a vbat scale and offset calibrate parameter would be nice. In the above measurements, the schottky diode to the right of the main board battery socket is still in the circuit. So the formula being used to report the battery voltage seems to be doing a good job of implementing the offset due to the schottky as well as the scale of the battery voltage. While experimenting to get the shutdown parameter save operation to work at low voltages, I put a short across the schottky, which raises the voltage available on the main board by about 0.35v, and makes it easier to keep everything working at the low voltage end of the Li-Ion cell. But with the schottky shorted, the battery monitor reports the battery voltage as 0.32v high (no surprise since the formula includes an incorrect offset). In a situation like this, an adjustable offset would be nice.

I have not had a failure of the transmitter to turn off. I ran more tests down to 2.8v with the 560K resistor reduced even further to 240K, and it now saves configuration at shutdown even at 2.8v