http://www.ebay.com/itm/25W-High-Power-300-OHM-Wirewound-Potentiometer-Rheostat-Variable-Resistor-US...
Voltage setting resistors. With a multi-step single stage switch. I purchased several of them. Gold contacts. To be used on my son-in-law's Click-o-watt to be.
The power supply does not issue a totally accurate unloaded voltage. Disconnected from a battery, the voltage will be .12 to say .24 volts higher.
So I want to calibrate the voltage steps right on the nose. And using a tiny 10-turn Bourns pot is a PITA.
So I got lazy and have just ordered the above to help my fumble fingers. Big, clumsy, and insanely easy to work with. Just keep the resistance ring and carbon contact on the rheostat clean and it's a great aid in pre-selecting resistor values.
Here is the way things are going to work...
The power supply is only useful for battery charging purposes from 200 ohms down to say 50 ohms control resistance. 11-volts high resistance is not needed (nor anything close to that) nor do I need precise voltage control above say 14.8 volts.
Let's give the control good span between 13.1 volts and 13.8 volts. 9-steps. Two optional steps for voltage settings above 13.8 volts. Since Jesus has a flooded marine battery one of the two optional steps will be 16.0 volts WHICH THE MEGAWATT CAN DO
An ON/ON switch is incorporated into the controls. And it is wired IN SERIES with the click-click-click switch. One side of the ON/ON switch is a direct connection. The OTHER connection has a BIASING 10 ohm resistor.
The output wires from the switch lead directly to the click-click-click switch. From the switch to a tiny perforated circuit board 12 22 gauge wires jump 4". The precision resistors are soldered onto the board. The board permits EASY coupling of resistors in series to attain EXACTLY the resistance value that the real-life rheostat test proves to be valid for exact pre-setting of Megawatt finish voltage.
The 10 ohm biasing resistor is there the help E=MC2 achieve reality. It will noodge voltage upward by a tenth or so.
My son in law has an eighth grade education and the 10-turn pot bothers him. So we are going to do "McDonalds Cash Register" ergonomics and label each of the switch clicks. Fine tuning for temperature. A top charge setting, then a another switch with bright flashing LED and piezo chime that is resistor set for equalization. No worries. The charger has a 12-hour intermatic spring wind up timer. I have already found an 800 ma 120 volt 13.4 volt (with a group 31 RV battery) fixed transformer style power supply to go inside the click-o-watt.
The 5 amp ampere regulator is a 12 volt 50 watt light bulb in series with the ClickOwatt battery charging cable clamps.
All he has to do is keep the damned thing out of the clutches of tropical beach salt laden air...
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This is Jim In Denver's, reconstituted Megawatt. It now has been significantly modified as per photo and unseen components. New Panasonic primary and secondary capacitors, 80-ampere rather than 30 ampere rectifiers, 145% higher capacity choke, quintuple (500%) increase in fooling airflow. A straight to board elimination of OEM potentiometer, and highly modified transient suppressor network inside. The unit now is a 56 constant ampere power supply. It's moniker is THE HYPERWATT
