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Author Topic: Electronic mixer for two motors  (Read 6391 times)

chris1

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Electronic mixer for two motors
« on: January 10, 2015, 12:48:28 PM »

Hi all,
Trust you've all had a good festive season.  Ive practically finished my current build, a Billings Kadet motor boat, and soon moving onto my next one, a Robbe Najade, which i am converting to twin, counter-rotating, screw, as per full size.
I would like to have independent throttle control at 'idle' to be able to maneouvre as per full size.  What i need is an electronic mixer which will do the following:
Throttle stick at neutral - using port rudder will give reverse on port motor and forward on starboard, throttle limited to say 10% of maximum, and proportional. This mic should ideally eliminate rudder control.
If throttle stick is moved away from neutral, whether forward or astern, the mixer should be disabled (i.e. both motors work together) and rudder control reinstated.
Just to make matters a bit more complicated i will be using brushless motors.
In a nutshell i cant find or afford an f14 navy radio so would like an electronic mixer to do the job.
Any ideas who can provide this?
Thank you.
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inertia

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Re: Electronic mixer for two motors
« Reply #1 on: January 10, 2015, 02:53:19 PM »

Chris
There are relatively few electronic motor mixers commercially available and I can tell you that I'm 99.99% certain none of them will do this. Unless you know someone who is proficient at circuit design and PIC programming I suggest you use tank-steering. You don't need a fancy twin-stick Robbe Navy tranny either - a throttle-return spring for the other Up/Down stick would be far cheaper in the long run.
Dave M
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Subculture

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Re: Electronic mixer for two motors
« Reply #2 on: January 11, 2015, 07:20:18 AM »

inertia

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Re: Electronic mixer for two motors
« Reply #3 on: January 11, 2015, 08:53:20 AM »

A clever guy - I stand corrected!
DM
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Mankster

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Re: Electronic mixer for two motors
« Reply #4 on: January 11, 2015, 09:50:57 AM »

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Re: Electronic mixer for two motors
« Reply #5 on: January 11, 2015, 10:29:45 AM »

I use this http://www.componentshop.co.uk/p40d-marine-motor-mixer.html


Obviously it won't do the job or DM would have recommended it  :-X :-X


Ned
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inertia

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Re: Electronic mixer for two motors
« Reply #6 on: January 11, 2015, 12:52:44 PM »

No, P40D won't apply less mixing automatically with an increase in speed like Alan Bond's design does. It will, however, provide four different levels of mixing which you can set with an on-the-board switch according to the type of model you have (e.g. fast launch or workboat). From reading the article it doesn't look like the AB unit is commercially available just yet.
DM
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chris1

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Re: Electronic mixer for two motors
« Reply #7 on: January 11, 2015, 02:27:52 PM »

Thank you gents. It looks like the Alan Bond mixer will do exactly what I am after, pity it doesn't seem to be available commercially.  I'm not sure i can assemble the circuit myself but will give it a shot. Thanks.
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Shipmate60

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Re: Electronic mixer for two motors
« Reply #8 on: January 11, 2015, 02:44:11 PM »

One company that PMK (For those that remember) had a lot of time for.
I see the mixer has been upgraded so not sure if suitable for only 3 channels.


Bob


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dem555

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Re: Electronic mixer for two motors
« Reply #9 on: January 11, 2015, 03:23:31 PM »


just for information.


the description of the unit @,


 http://www.srcmbc.org.uk/ht_afb_ruddermixer.php


 is not the same as the kit available from,


 http://www.technobotsonline.com/rudder-mixer-by-alan-bond.html
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Re: Electronic mixer for two motors
« Reply #10 on: January 11, 2015, 08:28:49 PM »

email alan. he is producing a limited amount for sale. i think 20 units. he needs people to test them. he will tell you the price
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Subculture

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Re: Electronic mixer for two motors
« Reply #11 on: January 11, 2015, 10:43:22 PM »

Good catch. I didn't spot he'd updated the design, they used to be the same.

afb

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Re: Electronic mixer for two motors
« Reply #12 on: January 12, 2015, 10:37:36 AM »

Chris1 has alerted me to this thread, so as the designer of the mixer in question I'll try and clarify the situation as best as I can.

Firstly, to be pedantic, my mixer doesn't do *precisely* what Chris specifies. In "dynamic" mode the mixing isn't disabled immediately upon leaving (throttle) neutral, but instead tapers off linearly from 100% as the speed increases finally reaching 0% at some user set speed. The range of setting (by potentiometer) of this cut off point is continuously adjustable from 30% of full speed to 100% of full speed. Also rudder control is retained in neutral, as I find this significantly improves the turning action on my tug though I've been given to understand that in real life a twin motored boat when stationary is manoeuvred on differential throttle control alone. However, the *spirit* of what Chris wants to achieve is addressed by my mixer and I see he recognises this in a later post.

But the whole point of my offering this unit on a trial basis prior to it becoming commercially available (from Technobots) is to tweak the design to what people *need*  rather than just offer what works well for me. My beamy tug isn't a high speed Najade and neither is it a long thin battleship with scale sized rudders that don't work very well. So if the majority of trial users find they need more or less adjustment of a particular feature and it doesn't compromise the remaining users, then consider it done! As I say in my 6 page PDF file on the SRCMBC website, any software mods resulting from the trial will be offered as a free upgrade (by chip swapping) to participants of the trial so there is no risk in being a guinea pig.

A better solution to meet Chris's *exact* requirement (and here I shoot myself in the foot) would be for him to use my mixer in "static" mixing mode, set the mixer gain to his desired 10% (in static mode it's continuously variable from zero to 100%) and connect the rudder channel of the mixer to a spare channel of his receiver. Then use that spare channel only when at zero throttle in much the same was as you would use a bow thruster - even the rudder doesn't move as he specifies!

This of course requires that you sacrifice a spare channel that you may prefer to keep for controlling other features whereas my "dynamic" mixing was developed to have the best of both worlds, keeping rudder control simple and seamless from zero to full speed.

So how effective is this "dynamic" mixing? Well, at the Alfold show last year I demonstrated a prototype of this unit and after trying my tug in "dynamic" mixing mode on the water for himself a member of Swiss Cottage MBC was sufficiently impressed to buy 5 units to equip his fleet. After installing the first unit in his Drumbeat of Devon he took it to show his club members and they promptly ordered a further 8 units! Since the (enhanced) trial unit was announced they've taken 4 more.

I plan to be at Alfold again this year, plus Beale Park so any of you are similarly free to try it out for yourselves. Other show suggestions in the southern area are welcomed for consideration.

As explained above the mixer is not yet available from Technobots and is not to be confused with what was described as my "kit" for a very basic  DIY V-Tail mixer that has been on Technobots site since 2010 or thereabouts - well spotted dem555. In fact the old unit not a kit but just a programmed microcontroller chip and the rest is up to you (parts list and build instructions on their website) - whereas today's offering is a ready built and tested production quality PCB (see attached photo and note the Technobots branding) and only differs from the final release in that you need to make your own access holes in the supplied box and you don't get a pretty label or a printed instruction leaflet - instead you download the aforementioned PDF file from the SRCMBC website.

I still have some of the 20 trial units left for which I'm asking 30, inclusive of 1st class signed for postage in the UK. Quite what Technobots will be asking for them later on I don't know.

I'll keep an eye on this thread from now on and contribute as necessary.
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hollowhornbear

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Re: Electronic mixer for two motors
« Reply #13 on: January 12, 2015, 01:06:35 PM »

Alan I have sent you a PM.
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afb

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Re: Electronic mixer for two motors
« Reply #14 on: January 12, 2015, 01:09:07 PM »

Already replied to your e-mail address
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mrlownotes

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Re: Electronic mixer for two motors
« Reply #15 on: January 12, 2015, 01:44:28 PM »

A trial request PM sent.
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Bintur Ellenbach

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Re: Electronic mixer for two motors
« Reply #16 on: January 12, 2015, 02:49:33 PM »

PM reply sent
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chris1

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Re: Electronic mixer for two motors
« Reply #17 on: January 12, 2015, 09:23:39 PM »

Brilliant explanatin Alan, thank you.  I've emailed you for an order.  I come from an rc plane background so will be using 'stick' radio with 4+ channels.  If i've understood correctly, i can use two separate channels for directional control.  So, left stick for throttle and mixer rudder control, and right stick for actual rudders, bypassing the mixer unit completely?  I can confirm the info you have been given re full size boats (I am a part-time charter and delivery skipper), at least for shaft-driven boats (boats with outdrives are different to handle).  Therefore if i bypass the mixer for the actul rudder servo, and use the left stick for the mixer, i should in theory have what i am after.  Mixer fadeout could be set to 0 in static mode too i guess. 
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afb

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Re: Electronic mixer for two motors
« Reply #18 on: January 13, 2015, 08:03:37 AM »

Yes Chris, the stick assignment you give is correct, but it might be clearer if you leave the "rudder" word out of the left stick description. There is NO mixer fadeout in static mode - it is fixed at X% mixing across the entire speed range, where you set X= 0 to 100% to suit the boat - that's why it's called static mixing, the percentage doesn't change with speed.

I've been wondering why you suggested 10% mixing when stopped - maybe as a skipper of real boats you use about that much throttle for manouvreing, but this is a 1:15 scale boat operating in 1:1 scale water and I think you'll need considerably more. In which case it might be worth trying the dynamic mixing mode as at higher speeds, depending on its setting, there will be less or zero motor steering unintentionally applied if when adjusting the throttle you fail to move the stick precisely in the vertical plane only. Anyhow, the option switches give you the opportunity to find out which works best for you.
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inertia

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Re: Electronic mixer for two motors
« Reply #19 on: January 13, 2015, 08:16:35 AM »

Using this stick assignment (i.e. three channels) it follows that you don't need any particular mixer to achieve the same effect; just one which has user-defined degrees of mixing. A P40D would achieve much the same result, then (phew!).
A problem would occur if you also wanted to run a bow-thruster, as do many people with modern tugs and workboats. I can't see any easy way around that except perhaps using a Tx with a rotary control on the front e.g. Futaba 6J.
DM
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afb

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Re: Electronic mixer for two motors
« Reply #20 on: January 13, 2015, 08:38:04 AM »

Didn't I say I was shooting myself in the foot when I suggested it Dave!
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inertia

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Re: Electronic mixer for two motors
« Reply #21 on: January 13, 2015, 09:23:30 AM »

It takes a top bloke to share a tip like that when he knows that 'the competition' is watching! Seriously, Alan, many thanks for this idea - I should have got there myself a long time ago.
Your new mixer looks just like all your other designs -  user requirements and design parameters clearly thought out; circuitry neat, cost-effective and well presented. If I had a twin-motor model I might even buy one just to compare it with the venerable P40, but all my present toys are single-screw. Maybe next time?
Dave M
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Re: Electronic mixer for two motors
« Reply #22 on: January 13, 2015, 10:20:37 AM »

Thank you for your kind words Dave - and I think you're wonderful too! -  years of experience in the hobby with tons of sage advice that as a newbie I'll never be able to match!

Perhaps to clear any misconceptions, I am NOT Technobots, they were just a local friendly firm and we agreed that I could market through them. But alas, they are local no longer, having just moved to Rugby over Xmas - perhaps to be nearer to you Dave?  My position is that this is just a retirement hobby that brings in enough to buy me a few toys to keep me amused.

If you are at either of the shows I mentioned, make yourself known to me and you'll be welcome to try out my boat as you don't have your own twin screwed boat with which to try a P40 comparison.  BUT WAIT - in the MMI review, the editor's strap line said "Alan (Senior) Reviews an Innovative Mixer for both Single and Twin Screwed Craft" - so clearly he knows something that has eluded the pair of us!


Now, back to the Bat Cave to continue work on my T100 Sound Unit <grin>
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inertia

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Re: Electronic mixer for two motors
« Reply #23 on: January 13, 2015, 12:16:17 PM »

Alan
I've sent you a private reply.
Dave M
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