These notes refer to the last issue of NCC controllers and will be kept reasonably up-to-date. So if you controller is older, the notes may be sequentially less 'correct'. Sorry about that, but we cannot keep instructions to cover all models of controller and if you are trying to change an old controller, sorry, but you are on your own. We can however can do a part exchange deal. See Service Charges.
All controllers made by 4QD are generally wide voltage operating range: limits are the operating voltages on the MOSFETs and the relays, and the power dissipation in the current source transistor used for the internal supply. See Pro, Scoota and NCC series controllers. Internal power supply and protection circuitry for a description of how the powering works.
This means that essentially the same controller may be used on 12, 24, 36 or 48v with only relatively minor changes so, for instance, conversion of a 12v controller to 24v is simple. However since this involves upgrading certain components it is not necessarily acceptable to modify a controller to work on a voltage higher than that for which it was originally specified. This particularly applies to the 48v versions where several components (mainly semiconductors) are changed but in general the 12v, 24v and 36v versions use the same components.
The VTX controller is not specifically here covered yet, but the principles are identical to the NCC. See also VTX series, additional notes.
In general the changes and components to check on all controllers are:
Other components
This resistor is fitted across two large copper lands on the component side of the circuit board, indicated by arrows in the diagram below. The link (also on the component side), indicated by the third arrow must be cut before fitting the resistor (or the resistor will be bridged out).
This is a very technical subject as the maximum allowable voltage depends on ambient temperature. Also at high currents the contacts get hot and some of this heat gets transferred to the coils, reducing the maximum allowable operating voltage in a complex fashion.
Also, if the coil is hot, then the 'must operate' voltage rises, because of increasing coil resistance. So this value is dependant on how long since the relay last operated and on how much current the contacts were carrying.
This all makes it impossible for us to give a definitive operating voltage range but, for most purposes, the allowable operating range will probably be something like 80% to 150% of the nominal voltage at 40°C, so the 12v coil should work from 9.5v to 18v and the 24v from say 19 to 36.
The internal supply is 9.1v. The current source requires at least 1v to operate, so if the supply voltage at the controller's terminals falls below 10v, the internal 9.1v supply will drop, reducing the value of the current limit.
Remember that the controller is chopping the battery current at 20kHz so the battery voltage cannot be read on a normal meter (as this will average the current/no current voltages) but you must look at it with an oscilloscope to see what it is when current it being drawn, at the troughs of the 20kHz squarewave voltage which will be present. Also - your battery lead inductance and resistance will add to voltage drops
These are the reasons we do not like high current 12v controllers!
The relay coil resistance is specified as 93 ohms for the 12v coil and 330 for the 24v coil (but in practise they tend to be nearer 389-390 ohms), so a resistor equal to the coil resistance will effectively double the operating voltage.
| Item | Order Code | Price List | Add to cart |
|---|---|---|---|
| 100R 2.5W | R25-100 |