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 Posted: Sun Apr 16th, 2017 04:40 am
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Michael M
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That would probably be a 'bad' thing.  I had to ask.  It's been a steep learning curve for me on this R/C stuff.



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 Posted: Sun Apr 16th, 2017 08:08 am
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davecttr
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Take a look at the efficiency graphs on the Pololu site. They are part of the information on each regulator. You will see boosting 3.2V to 9V gives you over 80% efficiency up to current draws of about 300mA. That means your single lipo battery of say 200mAh is actually equivalent to a 160mAh. You lose a bit in the voltage conversion magic. If you have a 2 battery pack delivering say 7.2v to the regulator the efficiency increases to over 90%.

Single battery operation is good as the Deltang Rx can monitor the battery voltage BEFORE it goes into the booster, a useful safety feature. It can with 2 batteries too but you are then into programming the Rx.

You can solder those little boards, I do with my arthritic fingers but I do get an occasional failure. Soldering is not my favourite task.

Before you know it you will become an expert!



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 Posted: Sun Apr 16th, 2017 04:08 pm
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Michael M
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I've gone ahead and ordered one of those regulators.  I've just got to try it out.



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 Posted: Sun Apr 16th, 2017 04:37 pm
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dan3192
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Dave, regarding the ability of the DelTang Rx to monitor the battery, I need some clarification. My understanding was that the low voltage cut-off is automatically determined at start-up depending on the number of batteries used, i.e., 3v for <4.3v, 6v for 6-9v, 9v for >9.1v. 

If you have some new information on this, it would be good to know as I had not planned on re-programming my Rx61 board for this.

Dan   

Last edited on Sun Apr 16th, 2017 04:37 pm by dan3192

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 Posted: Sun Apr 16th, 2017 05:34 pm
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davecttr
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Dan
The Rx will automatically monitor the battery voltage with the LVC (low voltage cutoff) set according to the voltage when the Rx is switched on. If you add a voltage regulator, say a 9V one, the Rx will set the LVC to 6V as you say, however the LVC will never operate because the output from the voltage regulator will not drop below 9V. Actually the Rx will close down but only when the battery is completely flat and suffered probably permanent damage.
Don't panic!
There is an option to connect the 'L' pad on the Rx to the positive INPUT of the voltage regulator. When you do this the Rx monitors the input voltage of the regulator not the output voltage and operates the LVC when the battery is depleted to a safe level. Neat!
There is a diagram on the Deltang site showing the connections.
So if you are using a 2S lipo pack delivering a nominal 7.4V to the regulator the LVC will operate when the pack voltage drops to 6V
You can also set the values manually using one of the Deltang programming devices. As my battery packs are made by me they do not used matched cells. So I manually set the LVC voltage to 6.8V for a 2S lipo and 4.4V for a 4 cell NimH pack. This ensures the batteries can't over discharge.



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 Posted: Sun Apr 16th, 2017 08:29 pm
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Si.
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Thanks again Bob. :thumb:

I checked out the DC-DC converter board.

Certainly can't complain about the size ! :shocked:



Watch out for 'drafts' ... It might blow away ! ;)


:!:


Si.


A great move, being able to use 1 battery.



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 Posted: Sun Apr 16th, 2017 10:38 pm
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dan3192
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Dave, we're "on the same page".

When I read your comment "...the DelTang Rx can monitor the battery voltage BEFORE it goes to the booster...It can with 2 batteries too but you are then into programming the Rx", I was confused since I was already aware of the 'L' pad connection upstream from the booster and had checked earlier with DavidT about using a 2S or 3S Lipo instead of a 1S Lipo.

The DelTang website has a sketch showing the 1S arrangement for my Rx61 in the v611 Features area (Sorry, I can't seem to bring the sketch over from my gallery...browser issues?). We just need to remember the 1S shown can be a 2S or 3S or even a 4S, depending on the Rx. So I'm relieved that no programming is necessary. Thanks for your confirming input.

Dan

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 Posted: Sun Apr 16th, 2017 11:45 pm
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Bob R
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Let me chime in again on the battery voltage monitoring points.
I have found that when using a 1S lipo and a Pololu 9 volt regulator I do not need any additional programming to monitor the battery voltage.  The Pololu regulator requires 3 volts to operate.  Below 3 volts it shuts down therefore preventing the battery from being "killed".  My experience is that when my engines stop running the batteries are at 2.9 volts.  That does not harm them and the charger will still recognize the cells and charge them.
Using anything other than a 1S lipo you do need to connect the RX L pad to the positive input on the regulator.
Bob

Last edited on Sun Apr 16th, 2017 11:46 pm by Bob R



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 Posted: Tue Apr 18th, 2017 01:58 am
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Bootlegbar
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My 1/35n2 critter started out as a HO Model-Power Plymouth.  I re-motored with a tape cassette motor.  It has a small start voltage so I do not need a step up converter.  Here is a picture that I think I have posted here before.  Shows the Air Hogs R/C board I was using at first.


 

The three pins sticking out are for my charging socket.  They came out of a computer board for a fan plug.  The Air Board only had speed control in one direction. One day looking at junk on Ebay I ran across someone selling a Deltang receiver, TX22 kit, I-max battery charger, extra micro plugs, and a small 7.4V battery for $60.00.  It was probably from someone that visits this forum.  Thanks if your reading this.







Here is my current set-up.  Deltang wrapped in the yellow shrink wrap. On-off switch is next to the charging pins. I will keep the cell phone battery because it works fine for me. I will save the battery from ebay for the next project.




Stephen. 


    

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 Posted: Tue Apr 18th, 2017 04:27 am
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Michael M
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Update:  One 3.7 LiPo worked but my critter just didn't seem to have much power.  Might have worked better in a railbus.  However; two 3.7 LiPo batteries in series provided sufficient power to pull a couple of cars.  :glad:





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