This blog leads on from the blogs Flight Controllers, see the section on APM/Additional Required Extras, (in particular Safetly Use CLONE APM Power Modules), as well as Low Voltage Warning for CC3D. There are varying reports that claim that these devices can pass the full battery voltage to the flight controller and fry it, but there are also others that say that this is scaremongering – so who is telling the truth? Also there are cheaper clones versions that lack certain components. This article explores both of these points.
Types of board
There are a couple of types of this board, principally the discontinued 3DR, see APM Power Module with XT60 Connectors Kit, and its direct clones (with or without the regulator and capacitor), and there are a couple of other Power Module derivatives (v1 and v5):
- 3DR – With regulator, which is on an additional “daughter” board, from APM2.6 2.5 2.52 power module/current module with 5.3VDC BEC
- 3DR – Without regulator, from RTFLYER POWER MODULE W/UBEC AND XT60 CONNECTORS
- 3DR – without regulator and capacitor, On eBay, 90A APM2.5 APM2.52 AttoPilot Voltage Current Sensor Module APM Flight Controller, £2.94, normally £3.13
- Power module (V1), this is basically the same power module but using a different (more integrated) circuit design, from Apm 2.6 2.5 2.52 Machtmodul mit 5.3v DC bec Bewertungen and Apm 2.6 2.5 2.52 Machtmodul mit 5.3v DC bec
- High voltage power module (V5) – again, the same power module but using a different (more integrated) circuit design, (from High Voltage APM Power Module with 3A UBEC):
- Another version, from APM 2.6 UBEC V2 (5.3V 3A) Power Supply Module, Voltage and Current Sensor (With XT60 IN & OUT)
- Geeetech, from XZN 3DR Power Module
The cheaper 3DR clones are missing two components:
There is a regulator board, for the (3+2) 5 pins, that attaches to the rear of the board.
Here is a close up view:
It should be possible to be able to get these regulators seperately
There is a tantalum SMD capacitor, as can be seen here (from High Voltage APM Power Module with 3A UBEC), note that the positive terminal is at the top, marked by the brown line:
The SMD capacitor is a 300 μF, 25 V (E rating = 25V), (see Online calculator – 3 digit capacitor, Reference on KEMET SMD Tantalum Capacitors, The Footprint Files – Electrolytic Capacitors and Installing Capacitor Kits) and has marked on it:
Arguments against worrying about the clones
I think you are unnecessarily scaring people. Yes, the switching regulator is absent and that’s why they are cheap. In fact I like them this way. I want to measure v/i but don’t need the reg. The capacitor is missing because it is only needed when the regulator is fitted. If you want the regulator then it easy to purchase and fit yourself. I have done this to three of mine and the caps are easy to get too. It is not possible for this circuit to apply full battery voltage to your APM if the regulator is missing. There is just no physical connection other than through a resistor and the normal failure mode of resistors is open circuit. In fact, a failed regulator is much more likely to short the battery to the APM as with a switching regulator there IS a direct connection to the battery through the switching FET and inductor. A shorted FET WILL smoke the APM and this IS a common FET failure mode. There is also no need to change the cable wiring if the regulator is not fitted. The 5V wire just goes nowhere which effects nothing.