Frequently Asked Questions:
How does the unit dim the lights (control the power)?
Reddford Technology DC light dimmers / power controllers utilize a common direct current (DC) power control technique referred to as Pulse Width Modulation. PWM for short. Our units cut the electric current into a series of pieces, or pulses. To control power (brightness - motor speed) we then determine for each pulse how long the current is turned on. If we turn the power on for 1/2 of the pulse time we have reduced the electrical power by 50%. The ability to change the on time of each pulse allows us to control, or modulate, the power output of the device.
How does PWM reduce power consumption?
Because we are controlling the power by turning a high efficiency transistor on and off and not wasting the unwanted power as heat like a resistance device, such as a rheostat, does. There is no significant power flow during the off period of each pulse. The energy used to control the transistor and related circuitry is very small in comparison with the amount used when a given pulse is on. Over any given time period dimming the lights (slowing the motor) yields a direct reduction in power consumption.
How about interference? I have heard bad things about PWM.
It is possible, but very unlikely that you will experience any interference problems. Although our products contain circuitry that operates at radio frequencies the power in those circuits is so vanishingly small that for all intents and purposes they do not emit RFI (Radio Frequency Interference). We have never received a report of an RFI problem. The very basis of PWM however means that all of the power carrying wires in a controlled circuit are being turned on and off rapidly. The power wires therefore can emit EMI (electro-magnetic interference). We have chosen a relatively slow switching frequency to minimize any problems. The frequency is simply too slow to be noticed by most other electrical equipment. The most common problem arises if other equipment share the same circuit breaker or fuse as the controlled device (lights, wipers, horns). The other equipment may sometimes be affected by the fluctuations in circuit voltage caused by the PWM. A simple rewiring (i.e. moving the affected equipment to a different breaker) will normally correct this problem. Other equipment can also interfere with our products. This mostly commonly occurs when powerful unfiltered battery chargers are pushing large amounts of current into deeply discharged batteries. These chargers can reflect the AC 120 hertz sine wave in their D.C. output. Our dimmers can sense the current ripple and cause the lights to flicker if they are significantly dimmed. This problem is normally self correcting when the batteries become recharged. This problem does not occur with wiper controls or the Ships Whistle Sounder.
OK, I probably will not have an interference problem, but what if I do?
Call us for help. Although rare, we have over the years developed a fair amount of expertise in this area and have thus far always been able to help our customers solve any interference problems related to our produces.
What do you mean when you say your products are Series Wired, and why is this a good thing?
In this instance Series Wired means that our parts only have one power wire in and one power wire out, like a switch, a separate wire to ground is not required*. This is good because it greatly enhances installation options. You can install the unit anywhere in the circuit, without having to worry about running a new wire back from the unit to ground. For many reasons the ground wires on boats are often ran in entirely different locations from the positive wires and grounds can be hard to locate and reach. *The auxiliary power supply that is used with the DCWE-20 Intermittent Wiper Control when it is installed with self parking wipers does require a ground wire so it is not technically series wired.
Your parts seem kind of expensive. What is up?
Quality and power. First, our products are designed and built to a standard, not to a price. You may be making a comparison with the AC dimmers for your house. They can be purchased for a fraction of the cost of our DC dimmers. The main cost difference is related to power. As you know electrical power is most commonly measured in Watts. Watts are a unit of power, and cannot be directly measured like Volts and Amps. Watts are calculated for electrical equipment as follows; Amperes (Amps) X Volts = Watts. For example 20 Amps X 12 Volts = 240 Watts or 2 Amps X 120 Volts = 240 Watts. Boats, RVs and cars for that matter, use low voltage systems (12 or 24 and in the past 32 volt) to eliminate any possibility of electrocution. This makes sense given the environment vehicles operate in, particularly boats which are subject to salt water spray and leaks. Amperes determine the physical size of electrical components. That is why the battery cables in you car, RV or boat are so big. It takes a lot of Amps at 12 volts to generate enough power to start the motor. Unfortunately, when it comes to electrical components bigger means more cost, sometimes very much more cost. The main power transistor in our products is rated at a maximum of 100 Amps. It alone costs more than the manufactures cost of a standard 600 Watt (5 Amp) AC household dimmer. A quick web search for 2400 Watt AC dimmers (our products would be 2400 Watts if they operated at 120 volts) returned a lowest price unit of $239.00 and even that is not a fair comparison because all of the 2400 Watt AC dimmers found were multiple