ESC for HK 250 GT

Hi,
a 12A ESC is imho to small. I recommend a 25-30A ESC
In my case I use a 40A HK blue in my HK 250 GT which is of course oversized, but it was available in my spare parts box..

Best regards
Chris

What about inbuilt BEC
2A or 3A ??

Hi all,

I just got my HK250 kits yesterday and I began to assemble different parts together. To my amazement, there is no instruction of how to put together. So don't be surprise. It is going to take you a long time to figure it out unless you have experience building heli before. My complaints is that when I went to check each nut and bolt to lock tide them, two of the screws to main gear holder were sheared off and skids are too flimsy one bended when I tried to straighten it out it broke. I am in the process of ordering some parts for replacement without even getting in to the air yet....

From "The Electric Helicopter Beginners Guide" Page 203:

BEC
Battery Eliminator Circuit.
On a nitro helicopter, there is a 4.8 volt "receiver pack" that powers the receiver,gyro,and servos. On an electric helicopter, we already have a very large battery which powers the main motor. However, the voltage of this main motor battery pack is typically more than 4.8 volts. So, the BEC will take the voltage of the main battery pack and regulate it down to 4.8 volts to power the receiver, gyro, and servos, This eliminates the need for a separate 4.8 volt receiver pack. There are two types of BECs: linear BECs and switching BECs. A linear BEC reduces the main battery voltage to about 4.8 volts by applying a resistive load and wasting the excess power as heat. This has two important implications: First, the current capacity of a linear BEC drops quickly as the input voltage rises. A typical 1 amp linear BEC can dissipate about 3 watts, so it can handle a load of 1 amp at 8 volts, but can only handle half this current, or 0.5 amps, at 11 volts. Second, a linear BEC is usually only about 50% efficient (or less) since it discards excess power as
heat. If a linear BEC becomes too hot, it will thermal shutdown and you will lose control of the model.

A switching BEC functions by rapidly pulsing the main battery voltage to create an average filtered output of 4.8 volts. This method of regulating voltage is more efficient than a linear BEC, so a typical switching BEC is 80 to 90% efficient. Also, it can handle much higher input voltages than a linear BEC (up to 35 volts or more), and the current capacity does not drop at higher voltages.

Note: Most BECs are rated for 5 volts of output. The extra 0.2 volts will not harm the electronics equipment. From an electronics point of view, a 5 volt regulator is easier to build than a 4.8 volt regulator since the parts are more easily available, so most BECs output 5 volts instead."

As an example:
- 4 off Corona 919MG Metal Gear Servo 1.7kg/ 12.5g/ 0.06sec @ an operating Voltage and Current of 4.8/6.0V & 200/240mA each, respectively for a total of 960mA
http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idproduct=11854
- 1 off HobbyKing GA-250 MINI-MEMS Gyro @ an operating Voltage and Current of 3.0/9.0V & 20mA (@5V)
http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idproduct=15318
- 1 off OrangeRx R610 Spektrum DSM2 6Ch 2.4Ghz Receiver @ 3.7/9.6 V (doesn't actually specify an operating current but it would be less than 200mA)
http://www.hobbyking.com/hobbyking/store/__25048__OrangeRx_R610_Spektrum_DSM2_6Ch_2_4Ghz_Receiver_w_Sat_Port_AUS_Warehouse_.html

Total Current draw (max) = 960 + 20 + 200
=1180mA (1.18A) < 2A (2,000ma)

It shouldn't matter whether the servos are either digital or analogue, just the current draw. Having said that a Digital servo tends to draw my current and may require an external switching BEC. So, from the above example the BEC in the ESC (@2amp) should be more than enough.

Edited by thesavage - 19/Jul/2012 at 3:01pm