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RC models by Robert Holsting

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  Electronics and RC .
There is no way around it: Without electronics and RC, this entire build will only be a showcase model, and that is not the target. A lot of thought should go into the electronics, and the RC configuration, as there are a lot of decisions to be made. Which features do I want my mobile crane to have? Which button controls what, and when? Should some functions be shared? What happens if this function is activated, while the crane is in this configuration? Fail to safety... How do I make the transmitter control my home made microprocessor based systems for the outriggers etc?
(The microprocessor based system will be described in a separate chapter.)

A second challenge is the fact that we need A LOT of channels! How do we solve that? Where should everything go...

Note: You use any and all Information 100% at your own risk.

  The radio.
I made a list of functions that I wanted my mobile crane to have, and when I counted the number of channels needed for that, I ended up at almost 20 channels. Rather that looking for a radio with that many channels, and spending an arm and a leg on it, I needed to look for other ways to accommodate that. I have a 12 channel radio (Graupner MZ24 w. telemetry), and I will now share how I got that to be more than enough!

  The receivers.
I use two 12 channels receivers, set up to operate in a mirror configuration. That means that when I operate for example channel 3, then both receivers will operate channel 3, and so on. One receiver goes into the carrier, and the other goes into the crane. I went with two receivers in order to reduce the number of electrical contact points between the carrier and crane.
It's important to notice that both receivers are always on.

  The regulator.
I have chosen the Servonaut M20+ because I like it. It has built in controls for the basic lights, and auto-throttle, which maintain the set speed until you either brake, or accelerate more. It also include a build-in 5A BEC for the receiver etc.

  Remote switches for lights.
Here I went with the CTI remote switches called PS4a. They go on the negative lead from stuff, and can handle a very wide range of things.
You can control four separate items, and they are toggled on / toggled off. (Switch function not momentary.)
Small enough to go anywhere, and in short brilliant.

  Remote switches for functions.
I will make a microprocessor based control system for the four outriggers and support legs, and I need to be able to control that from the remote.
I use two Conrad RC switches to give input signals to my outrigger controller, switch function momentary.

(The microprocessor based system will be described in a separate chapter.)

  Extra BEC for steering servos.
I have six strong steering servos (one on each of the steered axles), and they have the power to knock my receiver out cold if the all drain their max A. To solve that potential disaster I have placed several local BEC's for the steering servos, converting the 11,1V battery voltage to 5,5V for the servos..

  Servo reverser.
My crane has got eight axles, and six of those are steered. The two rear-most axles need to turn in the opposite direction compared to the other steered axles, so I got a servo reverser for that. The amount of mix can be adjusted, pretty nice.

   The battery.
I had NiMH in mind when I first began to build the crane, but have changed my mind towards LiPO.
I found a 5000mAH 11,1V battery incl. LiPO alarm, and I even share this battery with other models that I have.
Note: The battery is for driving only, and erecting the crane. Sustained crane operation will be supported by a power supply as this will demand a lot of energy.

(Later)   (RC components for the crane structure will be shown here at a later date.)




The functions and channels:
I made a table with the 12 channels, and started to match the functions of both the carrier and the crane to the controls, where it was most intuitive to look for them. (I would like to be able to change some of the switches with for example spring loaded switches, but that is not an option on the MZ-24.)

Graupner MZ-24  2,4GHz transmitter Carrier Crane Model select
Ch. Switch type Switch name *3 Item Function Item Function channel
1 Right stick, up/dn J1 - - (To be determined) Boom up/down 1
2 Right stick, L/R J2 6 x Servo Steering (To be determined) Turn crane left/right 2
3 *1 Left stick, up/dn J3 Regulator M20+ blue plug Acc / brake - - -
4 Left stick, L/R J4 Regulator M20+ clear plug M20+ control channel (To be determined) Winch out/in 3
5 on-off-on S1 Servo 3 spd. gearbox (To be determined) Boom out/in 4
6 on-off-(on) S2 - - (To be determined) Select next boom element -
7 on-off-(on) S8, up short PS4A, rc switch High beam - - -
S8, up long Cab lights - -
S8, down short Rotary flashes Rotary flashes *2 -
S8, down long Flashes on outriggers - -
8 on-off-on S7, up short - - PS4A, rc switch Work lights -
S7, up long - Cab lights -
S7, down short - - -
S7, down long - - -
9 on-off-on S3 Conrad switch A Outrigger control (To be determined) Y boom up/down 5
10 on-off-on S4 Conrad switch B Outrigger control (To be determined) Y boom angle 6
11 on-off-on S5 CTI Model selector "1" Enable carrier CTI Model selector "2" Enable crane -
12 Turn, 300 deg. DV2 Mix in radio Sets the gearbox in neutral. - -

*1: Note on channel 3: This channel cannot be shared, because routing it through any RC switches sends the M20+ into some error-mode, turning on all blinkers as a warning.. looks wrong.
*2: This rotary light is routed through the rotary switch between carrier and crane, thus no controller in the crane.
*3: "Switch name" refers to the name of the switch on the Graupner MZ-24.

As you can see I re-use channels, for example channel 2 are used for carrier steering AND to turn the crane structure... but how??

  Tadaa!!!! God's gift to model builders: The "Modell-Wahlschalter 7x1" from CTI. (Model selector)
I have two receivers, remember? I therefore also have two of these, but one is for model "1" (Carrier) and the other is for model "2" (crane).
They are both controlled via channel 11, allowing me to select if I should control the carrier or the crane. Any channels not routed through one of these model selectors are operational at all times. You select a model by clicking a number of times on the remote; One click turns on model selector nr. 1 and all other off, two clicks turn on nr. two and all others off. Simply brilliant!    (See the schematic 'RC configuration, carrier' for a block schematic.)

  This schematic show the on/off module configuration. ( pdf available by clicking here )
Note: The charge option is not valid for LiPO!

  This schematic show the light configuration. ( pdf available by clicking here )

  This schematic show the steering servo configuration. ( pdf available by clicking here )
(Also included on the 'RC configuration, carrier' schematic.)

  This schematics show the RC configuration of the carrier. ( pdf available by clicking here )

  This schematics show the flash system for the outriggers. ( pdf available by clicking here )

  This schematics show the boom rest switch. ( pdf available by clicking here )

Page about this: Click here.

  This schematics show the outrigger controller. ( pdf available by clicking here )
Software (G-code) for the Atmega available by clicking here. Remember to rename to "main.c" and run assembler.

Page about this: Click here.

(available later)   This schematics show the RC configuration of the crane. ( pdf available by clicking here later)


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