Voltage regulator help (Zener diode/resister)

[REVO-5309]

So I'm lookin at a lightweight voltage reg for my small rc glider. I have a turnigy 7.5g one ATM, but since I'm only going from 8.4v to 5 or 6v and only powering a micro 5channel receiver and 2x 5g servos I figure I can just use a resister and or a Zener diode.

I'm hoping to be able to keep the output voltage at roughly 5 or 6v constant.

Can anyone tell me what resister and Zener diode I need and exactly how to wire it up?

 

[Sixtysixdeuce]

Can anyone tell me what resister and Zener diode I need and exactly how to wire it up?

The problem with either one is that they don't really behave as voltage regulators; they are voltage reducers. A voltage regulator adjusts it's resistance based on input voltage and output demand.

A resistor will lower voltage by a constant percentage ("constant" to the extent that heat will reduce impedence in a linear fashion if not kept within range). Furthermore, you need to know your watt usage to determine the correct resistor for the desired voltage drop; tough to do when it will be constantly changing with servo load.

A Zener diode will reduce voltage by a fixed numeric value, whatever it's breakdown avalanche rating is. So a 3 volt reverse biased Zener will drop voltage by 3 volts, regardless of input voltage. It does not matter if your battery pack is putting out fully charged 8.4 or nearly dead 7.1, the drop will always be 3 volts.

There are some very small VRs out there, but most of them are meant for very low wattage circuits in digital electronics. If I were you, I'd calculate your peak wattage (amps * volts), add 20% or 30%, then go shopping. Check DigiKey.com

 

[REVO-5309]

Might just go with my turnigy 7.5g regulator.

How do those voltage regulators work? Do I need to run resistors with those?

http://m.jaycar.com.au/m_productView.asp?ID=ZV1505

 

[Sixtysixdeuce]

No, you wouldn't, but your draw would have to be <1A, and input voltage would have to be within spec.

Remember, a lot (not all) of the small transistor and IC sized VRs are meant to regulate low currents to a precise amount from a close amount. In other words, the transformer powering the digital electronic device (internal or external) supplies about 5V DC, but it can vary a little. These tiny regulators (that is a TO-220 housed unit you linked, only about 9mm wide and 4mm thick) will take that roughly 5VDC and keep it exactly 5VDC to prevent small variations from affecting the performance or integrity of fragile integrated circuits (IC, MSI, LSI, VLSI "chips"). This particular unit is actually designed to regulate down from a much higher voltage, but still at a very low current.

These 3 and 4 terminal micro VRs look like regular transistors, but there is more going on inside them:

 

[REVO-5309]

So will that work for me? I won't be drawing much power. Ill hook up my watt meter when I get home, but 2 5g servos and a micro receiver will draw sfa.

At the end of the day. I just need something light and simple.

 

[hamz9561]

Most pico (micro park flyers) us less than 1 amp for all the servos and the rx. The main draw on them is the ETC and motor. All of my micros use less than a 1000th battery. The largest is an 8850 mAh.

 

[REVO-5309]

Yeh. I have no motor or esc. And I'll be running a 180 or 300mah 2s pack