Meanwell S-350-12 12VDC power supply

ATX power supplies, as are found in most PCs and cheaply on eBay, shutdown in the event of a current overload (or short circuit) until the 120VAC input is power cycled (disconnected and reconnected). This is a reasonable response in the context of sensitive motherboard components. However, some AT units (e.g. ATR5) carry large inductive loads (kilowatt DC motors) which instantly kill ATX supplies due to their spin-up current surges. The Meanwell S-350-12 switching power supply resembles a...

High Current DC Connectors

Small diameter barrel connectors (1- to 2-pole, different sizes incompatible) are the ubiquitous low-current DC connector, supplying up to 2A.  USB Mini-B connectors supply only about 1.5A max (plenty for logic!), whereas reliable but bulky Molex connectors (2- to 26-pole) can handle 5A.  SAE 2-pole connectors can handle at least 5A, and are hermaphroditic (which simplifies charging, for instance). Servos often use a 3-pin connector, 26- to 22-gauge, where the third wire is a low-current signal ...

ETQ TG1200: Final Fuel Consumption Measurements/Analysis

Preliminary fuel consumption measurements for the ETQ TG1200 gasoline generator operating in the 0 to 600W range were published on 2009-12-23, along with a background of gasoline generator theory as applied to the TG1200. The interim has brought additional measurements and improved statistical analysis.  The fuel consumption [c] as a function of instantaneous power output [w] has been verified as reasonably linear [c(w)=pw+i] with idle consumption i=0.0830 gallons/hour, proportional consumpti...

Power Sources 2, or, Why ATR5 is powered by two combustion engines

Small garden tractors, such as ATR5-b0, are not designed to support heavy electrical loads.  Their engines contain integrated alternators to power headlights and maintain the starter SLA, with an output around 40 watts.  This might be sufficient for logic electronics, but actuation and lighting add at least 50 to 100 average watts.  Even optimally efficient CFL or LED headlights will add 35 watts, and the physical actuators (especially steering) will add another 30 to 60W average.  [For instance...

DieHard 27582 SLA unverified capacity function

Sears sells the DieHard model 27582 marine (deep cycle) battery for $130 (excluding core deposit). This is probably the cheapest chemical (Sealed Lead Acid or SLA) battery in its size range on the market in terms of initial cost ($ per Peukert capacity).  The 27582's total power output is not obvious, given that SLA discharge efficiency varies depending on instantaneous output current, significantly affecting the runtime between charges. The Peukert capacity C is defined as the total amp-...

ETQ TG1200: Preliminary Fuel Consumption Measurements

Unlike chemical batteries, gasoline generators consume a minimum amount of fuel even at zero current draw. [The battery equivalent is the inverter idle current, but this is typically only a few watts.] To a first approximation, internal combustion generator fuel consumption (liters per hr, c) as a function of energy output (kW, w) is linear [c(w) = pw + i], where the power-proportional consumption (p) and idle consumption (i) tend to be inversely proportional.  Manufacturers usually advertise on...

Power Sources, or, Why ATR3 is powered by a combustion engine

I am not inclined to work with combustion engines, given their vibration, heat, noise, and maintenance requirements.  Moreover, combustion engines have a significant zero offset in their fuel consumption vs energy output function; ATR3's engine consumes 1/3 gallon (1.25 liters) of gasoline per hour at idle.  Unfortunately, while electric motors can readily convert electrical energy to a rotary form, I am not aware of an alternative energy storage medium that can accomplish all three of the f...