Power Master
History
Mk I
PM Mk I was a full analogue speed control. It all operated from a single LM339 quad comparator, and could run at ~ 25 A continuous. Two trim pots were used to adjust throttle midpoint and span. It incorporated a brake which proved to be dysfunctional. Two in total were built, with 1 being used for ~2 years on a stock motored 1/10th scale with little problem, except for it was susceptible to dust and high humidity or water. The throttle trim used to wander under these conditions. Built in late 1999.
Mk II
PM Mk II was the first true Power Master. It was huge, 30 x 89 x 20mm. It was built for my son who had a passion for power. Easily handles 75 Amps and 16 V. First all micro controller based, but has no variable settings. The radio is adjusted to match the throttle positions. Two were manufactured, the first initially having some quirky glitches at some throttle positions. This one is still in use in a 1/10 Colt using 12 turn motor (not the motor in the picture). First built in Feb 2001.
Mk III
Pm III was the first programmable PM, the first ones having no anodising and only being programmable for throttle positions. Later versions were anodised, and included programmable ramping. The program also included glitch rejection and a fix for radios with long throttle/short brake spans. It measured 31 x 58 x 8mm. First built in August 2001, with a total of 9 manufactured. a slightly shorter version was made (1 only) in July 2002, when better Mosfets allowed the number of drive mosfets to be lowered from 5 to 4. 2 of these developed a problem with blown brake mosfets. This problem was cured.
PM IV was built because potential buyers were asking for a smaller package. It was the first to use a double sided circuit board, and is essentially a short PM III folded in half. It measures 31 x 27 x 12 mm. The program was changed so that ramp programming was achieved in a pulsed trigger (count) method instead of an analogue trigger position setting. A total of 6 made, 2 still available at a reduced price. Initial units would operate for a number of hours, and then develop a problem of occasionally shutting down output, which could only be restored with a reboot. i.e. unplugging and reconnecting to the battery. Subsequent circuit and program modifications removed the problem, which appeared to stem from the micro controller being capacitively coupled to the switched track on the other side of the board. All sold units were recalled and fixed with no further problems. First Built March 2003.
Mk V
PM Mk V is a completely revised board. It has a larger heatsink for mosfets and voltage regulator, and all power switching tracks have been kept well away from the micro controller. The package is smaller (29 x 26 x 12 mm) and the program has been updated to include initial brake, better ramping algorithm, and the ramping and initial brake programming sequence is now separate from the throttle position sequence. First in Sept 2004 with 14 built and sold with no problems.
PM Pro
Power Master Pro was a significant upgrade of Power Master Mk V. The upgrade was achieved by doubling all mosfets, so that there were 8 drive mosfets, and 2 brake mosfets. This gives an incredible upgrade of specifications so that PM Pro could handle 130 Amps continuous. Pity the wires prevented such current draw, but at least the on resistance was low. Only 1 ever built.
Mk VI
The introduction of higher performance mosfets has meant greater power than ever before. The lower "on" resistance means that heat build up at the speed control is basically non existent, except at the very top end. This has meant that the heat sink alloy case has been dispensed with, because in basic form PM VI can handle up to 95 Amps continuous. With heat sink case (optional) PM VI will handle 130A continuous, but there is not much point as the wires, connections and batteries will not. The greater performance of PM VI has meant that PM Pro is no longer an option. Extra noise suppression was also added. First built November 2005.
This page last updated Monday, 06 November 2006