ΓενικεSOME INFORMATION ABOUT REGULATORSς πληροφοριες  

The purpose of this article is to give a brief explanation of the regulator device used in RC systems.
First DO NOT confuse a regulator with a BEC which is something a bit different.
The Battery Eliminating Circuit is a device that allows you to power the receiver and the servos from the model's motor power battery.It is found in the majority of speed-controllers.

The most common and popular way of powering the receiver and the servos in a radio controlled model is by using a 4-cell Nicd or Nimh pack (4.8 V with a capacity around 800mAh) .
This is the standard RX battery pack supplied with the majority of RC systems and it is adequate for many simple model setups.
However there are applications where this simple 4.8 V battery pack is insufficient for a variety of reasons.

One reason is that, in some models we use many servos that demand higher currents from the battery, so we must use a battery pack of larger capacity in order to power the receiver system. But larger packs add to overall weight, which is not always desirable or allowed.

Another reason is that, during operation of the RC model, the battery voltage gets lower as time passes, resulting in less servo power and/or speed. This difference in servo power/speed is of course undesirable, as it affects the model's performance, especially if we participate in racing events.

A third reason is failure of one cell. If we have a 4-cell pack (4.8V) in which one cell fails, then we have the problem that both the receiver and the servos have to operate on less voltage, something lower than 4.0V. The results are disastrous since receivers can not work properly at this voltage.
An easy way to get around this problem is to use a battery pack with more than 4 cells, for example, a 5-cell pack (6V). In this case we may have a problem if our receiver and/or servos are not rated for 6V operation.

The fourth reason sometimes is that, in order to balance the model correctly, we have to position the battery pack at some distance from the receiver, thus using a longer battery cable. This results in increased voltage drop, especially under heavy current loads, which in turn means less voltage at the receiver's input.

One way to overcome the above problems is to use a 2-cell LiPo pack (7.4V) together with a regulator board in order to obtain the receiver's voltage supply.
We have to use a regulator between the pack and the receiver because RC receivers operate in the 4.8V - 6V voltage range only. So with the aid of the regulator board we step down the 7.4 V voltage to the desired one, within the 4.8V - 6V voltage range.

The regulator must be able to withstand the maximum current drawn by the receiver-servo system keeping a constant output voltage. In this way we have a stabilized voltage supply which guarantees that the receiver-servos system will work with efficiency, from the beginning to the end of the session.
An important parameter is the so called dropout voltage. This determines the lowest voltage that can be applied to the regulator's input and still have the desired voltage at the output. This dropout voltage is usually in direct relation to the current drawn by the receiver-servo system and should be as low as possible.

Example: A regulator with an output of 5.5V having a dropout voltage of 0.2V @ 3 Amperes will maintain its output stable at 5.5V as long as the powering battery pack is above 5.7V. Below 5.7V the regulator's output voltage @ 3 Amperes will be 0.2V less than the input voltage.

Another issue is heat generated in the regulator. For analog type regulators this is in direct relation to the input-output voltage difference, and the current drawn through it. This heat is higher with a larger input to output voltage difference.
On the other hand, switching regulators have minimized heat problems, but at the cost of increased Radio Frequency noise. This RF interference is created because of the way a switching regulator operates .It maintains a stable output voltage by abrupt current pulses through an inductor-capacitor-diode topology and this generates RF noise which sometimes desensitizes nearby receivers or confuses sensitive electronics.

Now, all information given above may seem difficult to be applied in the selection of an appropriate regulator to suit one's needs. So in future articles we will try to give examples that clarify the regulator issue.

 

 
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