2012‐8‐22 RCGROUPS ADDING FRSKY TO A SPEKTRUM DX8 Mini How‐To | JJ604
Adding FrSky to a Spektrum DX8 Adding FrSky to a Spektrum DX8 This brochure was photo’d and produced by JJ604 Copyright by JJ604. PDF made by Kai. Original: http://www.rcgroups.com/forums/showthread.
2 Adding FrSky to a Spektrum DX8 Table of Contents ADDING FRSKY TO A SPEKTRUM DX8 ................................................................................. 1 ADDING FRSKY TO A SPEKTRUM DX8 ................................................................................. 3 SHORT ANSWER FOR ELECTRONICS TYPES .................................................................................... 3 LONG ANSWER .....................................................................................
Adding FrSky to a Spektrum DX8 Adding FrSky to a Spektrum DX8 The FrSky 2.4 system is popular because of its extremely reliable radio link and growing range of telemetry options at a reasonable price. They currently make plug in modules for suitable modular transmitters plus two add‐on DIY modules that can be installed internally (DTH) or externally (DTH‐U) on any transmitter.
4 Adding FrSky to a Spektrum DX8 NiMH with the alternative 7.2V LiPo pack which is sold as an accessory (or the much cheaper HobbyKing equivalent). The DX8 is designed for it, includes the correct charge circuitry and it will double the operating time as well. The DX8 low voltage alarm will go off long before the FrSky stops functioning. The signal problem is a little more subtle. If you look at the signal coming out of the DX8 trainer jack it looks like Trace 1. The “0‐“marker is zero volts.
Adding FrSky to a Spektrum DX8 Trace 1 Trace 2 JJ604 5 5
6 Adding FrSky to a Spektrum DX8 Trace 3 JJ604 6
Adding FrSky to a Spektrum DX8 Build Providing Power 1. Change the Tx pack from a 4.8V NiMH to the alternate 7.2V LiPo one – SPMB4000LPTX. Either the Spektrum original or the HobbyKing equivalent will work fine. I used the latter. 2. Add a second battery connector to the new battery for the FrSky module. The simplest way is to use a good quality servo extension lead cut to length. Solder the normal connector (the smaller end) to the battery lead as shown in NewBatteryWire*.
8 Adding FrSky to a Spektrum DX8 Providing Signal 1. You will need either a stereo or mono 3.5mm jack and a 47k resistor. Also a small on/off switch for the power supply to the DHT. I chose a good quality slide switch as this is the main On/Off switch for your transmitter when in FrSky mode but a toggle switch is simpler to mount and operate and is probably a better alternative. It is shielded by the jack when in use so is well protected from accidental movement. Choice is yours.
Adding FrSky to a Spektrum DX8 body is the ground (Black wire – also the power ground). On a stereo jack the centre band and its third wire are not used and must not be connected to anything. Many stereo leads use a red wire for the tip, white for the centre and the outer copper braid for the body but you should check this with a multimeter to be sure. 3) You need to connect the 47k resistor between the PPM signal wire and ground.
10 Adding FrSky to a Spektrum DX8 Putting it together 1. The first step is to trim a bit off the end of the DHT indicator board as otherwise it will just touch the works inside the transmitter and stop it closing properly. Cut off up to the mounting hole on the switch end. See BoardTrimmed*. 2. Open up the DX8 with the battery unplugged and removed. First peel off the two contoured rubber back grips. They can be pulled up and away from the thick end.
Adding FrSky to a Spektrum DX8 11 3. Fit the DHT indicator board inside the back next to the Aux knob pot and as far forward as possible. Mark the position of the LED, measure the distance and drill a 3mm hole for it from the outside. Check it is in the right place then drill a 3.5mm hole for the bind button at the correct spacing. Drill a 6.5mm hole for the aerial connector next to the Trainer switch. See ThreeHoles*.
12 Adding FrSky to a Spektrum DX8 5. Attach the DHT with some double sided tape, route the wires neatly, and thread the DHT Mode wire through the battery compartment hole. The switch itself sits in the battery compartment since I only use telemetry receivers and will only need to access it for firmware updates.
Adding FrSky to a Spektrum DX8 6. Reassemble the transmitter making sure that none of your new wiring can touch the control pots or their wires when they move. I had a puzzling interaction between the two controls on one stick until I figured this out. 7. Fit the battery and DHT Mode Switch and the new connector into the battery compartment. BackView* and BatteryCompartment* show how it all fits.
14 Adding FrSky to a Spektrum DX8 8. Attach the FLD‐02 display. I used a wedge of rubber cut from the packing a brushless motor came in and 3M Outdoor double sided tape. See DisplayMounting*. You could also use the FrSky custom handle mount.
Adding FrSky to a Spektrum DX8 Using It 1. For the original DX8 DSM2/DSMX just use it as normal leaving the new power switch off and the jack unplugged. A bit of Velcro on the jack makes a handy storage. 2. For the FrSky, leave the DX8 off, plug in the jack, wait till the DX8 starts up in Slave mode then turn on the new power switch. Bind the FrSky receiver as usual using the new power switch and the FrSky bind button. Never turn on the DX8 main switch if you are in FrSky mode. 3.
16 Adding FrSky to a Spektrum DX8 2. Boost the voltage. All we need is a method to boost the NiMH pack to a steady 6V. Unfortunately the 6V BECs we use for models won’t work as they are all voltage reducers and will not output a voltage higher than the input. A similar circuit can be used as a voltage booster though and they are sold as USB‐>6V converters which have adequate current capacity of 300mA or more. http://usb.brando.com/usb‐to‐6v‐volt...2c042d015.
Adding FrSky to a Spektrum DX8 Voltage Booster This is in case anyone else is doing a conversion with a Tx that has a 4.8V pack. If you want to add an additional RF module to the DX8 (like an FrSky or similar) the 4.8V standard battery is a problem since many of them need 6V or more. You can change to the 7.2V LiPo battery which is what I did but there's another option. This little voltage booster* is $3.
18 Adding FrSky to a Spektrum DX8 pack in 42 years. Even with the tiny SMD LED it isn't much more than the NiMH self discharge rate. 4. Change the battery The DX8 has actually been designed to use either a 4cell NiMH or a 2cell LiPo. If you replace the original battery with the SPMB4000LPTX LiPo 4000mAh alternative the problem is solved. The transmitter already contains the LiPo charger and you alter the voltage cut off alarm in the system setup. Minimum voltage is then 6.
Adding FrSky to a Spektrum DX8 with no switch connected is 2‐way. You will have to take the case apart if you ever need to do a firmware update and re‐attach the toggle switch.
