RC Nitro engine plug, what is the amp needed?

 


 power a plug form model engine, I have do some test with my power supply:


Bearly heated at 2.21A



1.19V 2.5A seems fine


1.39V 2.79A seems the be limit.


Target:

 make a Arduino controlled constant amp controller 

There are lot of DC DC converter, claim to have 3A, but it's the chip claim.

MP1584 is used in most small boards.(2338 is latest chip recommended by MP)





It's easy to see that the inductor is often not big enough, schematic required 10uH, but most of those small boards are only 4.7uH.

Plan is to 
1. add enough inductor.(not sure what is the diode for? it's not on the schematic ) to see if it would provide enough Amp.
2. use arduino board to measure current and with DAC to put voltage on the feedback pin. in order to light up at 2.5A.
3. Using enable pin to on and off the device.

Test 1

I did try to control a mosfet with arduino and use INA219 to do current control,
but the N-mosfet I use D4184 is not designed for low gatedrive. 
It has oscillation problem.



Test 2

I have some cheap small DC-DC module with MP1584, claimed to have 3A. I did a test. But it did not work out, the chip get heat protection at about 1.9A

it was ok at about 1.7A

But goes shut down at 1.9A about 100 C





1st conclusion: 

these 3A claimed chip, with integrated mosfet, will not work out in my application.



Turn into bigger board : XL4015 rated at 5A
I tested these before with .21 engine plug, it works. But you need a switch to control on/off.
Check on the data sheet, it seems you can turn off the converter with a TTL 3.3V on the feedback pin with a diode, 1N4148
But not all the data sheet has this page, so I guess, not every chip                                                                                                                                                                                                                                                                                                                                                                                                                       out there has this function



The idea is to use DAC to control voltage/current and turn on off the board.

LM2596 is another popular IC, it has adj version and a on/off pin, lower 1.3V on pin5 turn ON, higher than 1.3V turns OFF


I tested a LM2596 module on hand, desolde from PCB and connect to 3.3V, it will turn off the module
But since the requirement is below 1.3V, so if it's float, the module still out put.

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