To provide more run time with the conversion to petrol & spark ignition, I have also upgraded the on-board electronics supply to compensate for the extra ~650mA draw of the ignition module.
This modification is centred around a 3S Lithium-Polymer battery pack, providing a nominal 11.1v to a voltage regulator, which steps down this higher voltage to the ~6v required by the receiver & servo electronics.
The regulator, shown above, is a Texas Instruments PTN78060WAZ wide-input voltage adjustable regulator. This module has an exceptionally high efficiency of ~96% at it’s full output current of 3A. The output voltage is set by a precision resistor, soldered to the back of the module, in this case 6.5v. Standard RC connectors are used on the regulator to allow connection between the power switch & the radio receiver.
Everything tucked away into place inside the receiver box. The 3S 1000mAh LiPo fits perfectly in the space where the original Ni-Mh hump pack was located.
The completely stable output voltage of the regulator over the discharge curve of the new battery gives a much more stable supply to the radio & ignition, so I should experience fewer dropouts. Plus the fact that the engine now relies on power from the receiver pack to run, it’s a built in fail safe – if the power dies to the receiver, the engine also cuts out.
To help make my system more efficient, a pair of switching regulators has been fitted, the one shown above is a Texas Instruments PTN78060 switchmode regulator module, which provides a 7.5v rail from the main 12v battery pack.
A Lot like the LM317 & similar linear regulators, these modules require a single program resistor to set the output voltage, but are much more efficient, around the 94% mark at the settings used here.
The 7.5v rail supplies the LM317 constant current circuit in the laser diode driver subsection. This increases efficiency by taking some voltage drop away from the LM317.
The 7.5v rail also provides power to this Texas Instruments PTH08000 switchmode regulator module, providing the 5v rail for the USB port power.