Showroom **RIP** - 6DOF project using 12v DC Motors, Sabertooth 2x60's (was MM's) and Arduinos + OSW

Hi @SilentChill my 2 Server PSU are linked in parallel with blocking diode fitted to each output to stop power going back to the each psu so far have to say touch wood no issues with them at the moment , a friend of mine suggested you may need these blocking high power blocking diodes in series with each power supply output just a thought

Don't happen to have a link do ya ?

In order to isolate psus I would use a bridge rectifier instead. Does the same thing as a single diode and also protects if you connect a psu with a reversed polarity. http://m.ebay.co.uk/sch/i.html?_nkw=bridge+rectifier&epp=24&_pgn=1&actrack=true

never had thought we could use it like that.
i know you are referring to the metallic one(may need a heat sink on it for high amps) but i am showing this photo just for the symbols.
it should be wired like that right?

If it's like this, then yes.

http://www.ebay.co.uk/itm/Vishay-VS...V-70A-200ns-/322224872688?hash=item4b06195cf0 hi @SilentChill I used 2 of these in my setup will post picture of my connection if needed cheers

Another way to connect the bridge rectifier just occurred to me. Since we are not using it to convert AC to DC, we are only using half of the bridge. Therefore, with the wiring as shown above, the other half of the bridge only works when we reverse the polarity leads from the power supply. But still only half of it is being used, just the other half. Therefore, we can instead wire it as shown below to use both sides of the half bridge at the same time and double its stated amperage capacity with the only trade off being that the power supplies are no longer protected if you mistakenly connect its power leads backwards. (note: while the diodes will be able to handle double the stated current rating, this assumes that the leads being used internally are large enough to also handle the additional current)

Basically it just uses it like a single diode.

Note:The diodes that are in series serve no useful purpose so you could also wire it so it only uses two of the diodes in parallel. Then if a diode goes bad you can just swap over to the remaining good diode so its like having a built in replacement for each diode. Of course, you could also leave it wired as shown and just eliminate a diode from the circuit if one goes bad.

Awesome thanks @wannabeaflyer2 and @BlazinH. Think I will go with the bridge rectifier as they are cheaper I will have to get 12 of them to stop any back current going from each MM hopefully that will solve any issue if there actually is one

Did some more testing last night and seems kinda ok and in game the most current I was getting was between 20-30 peak amps so realistically 1 MM per motor should do but they as soon as I got onto Dirt Rally a couple of the MM's were shutting off.

The rig has a big range of movement and I only have everything set on 20% . I just want the thing to work properly so I can get playing !!!!

I'm curious what game you were using when you tested 20-30 peak amps, No Limits? If so, Dirt Rally, if its tuned good, will very likely pull more peak amps than that and it will fluctuate at a higher frequency also.

Yeah in NOLimits there are some terrible twists and turns this going from the bottom of actuator and reversing so I think it was a half decent test.

I have battered it in smc3 utility and pulled over 50amps but the way I did it no games would be doing that

I have put some 1uf caps on the Pots seems to of sorted the noise out quit a bit. still not silent but much better

You may be right but I was thinking of heaving in Dirt Rally. On my rig it shakes the hell out of you and can pull some high current but short duration peaks.

ps My heave is set at 1.45

Hi @SilentChill hmmmm caps on pots , could you post pic of there connection to the pots and value selected , im one o those guys that is happy with mechanical stuff but electronics needs work LOL , not noticed noise on my rig but that may well be because I don't know how it manifest itself during operation , it may be something I can add to improve my setup . the sim seems to hold position well with no noticable jitter but then again this may be contributing too the odd occasion of the pot losing position thing ... ( that assessment may be totally wrong on my part) but this coukd be something I should implement Cheers mate

Ok had enough of MM's I have upgraded to 3 Sabertooth 2x32 drivers. Hopefully I will have some big updates soon

@BlazinH I should of listened to you a long time ago when you were raving about these lol

Lol glad to see another sabertooth convert , you dun good kiddo , they may cost a bit more, but pay for themselves in service and factory support in no time , and nice levels of Internal protection , hell they have survived all my hamfisted mistakes and are still ticking, great choice .they May not be for everyone but damm they are good.

Watching this with interest.

EDIT: Lol, maybe not so much, $192 here in Aus..... Still it would be good to know the difference between them in terms of performance by someone who has used MM extensively. Can't say I've had the experiences that you have had "crosses fingers" hopefully I won't have to endure it when I re build my sim.

Hi matey, I have already asked questions from support and got quick replies. Im just praying they will work as the MM's I have just cant handle the hard reverses on these motors. If I weigh it up with what I spent now on MM's I could of bought 3 sabertooths, they cost me £93.98 each from www.robotshop.com so a little expensive but no more hassle reflowing and fixing bad MM's.

I think with the MM's I must just be asking too much of them and with running them in dual I think if one is just slightly faulty it throws the other one off somehow. I don't know but my days of MM's are gone lol apart from using them to power wind fans

Another good thing with the sabertooths is the amount of wires you need, only 3 wires from the arduino for 2 motors instead of the 16 with MM's.

Just awaiting delivery which hopefully fingers crossed maybe today.

"could you post pic of there connection to the pots and value selected"

hope you dont mind me answering that, the caps need to be across ground and aref (control). I used 0.1uf on mine and checked with oscilliscope, they make a big difference in smoothing the signal. maybe 1.0uf is better,i still havnt found time to work out how to calculate exact values needed. you need ceramic disc ones (not tantalum etc)

Theres some oscope pics here of the difference it made:
http://motionsim.freeforums.net/thread/149/uk-ac-powered-6dof-project?page=8

Thankfully you dont need to worry as much with DC, the amount of noise vfd's put out with AC is a pain in the arse.

I feel your pain @SilentChill - went through a similar process initially (its in my thread), but in the end was lucky enough to scrape together 12 serviceable units. I really wonder if the current crop of MMs are even capable of operating the same as the old batch, as I note that all my good chips had a 'R' printed in the top right hand corner of the chip . Anyway its good to know that there are tried (if relatively expensive) solutions if I have a failure in the future and cannot get any joy with replacements. I'm sure all your hard work will soon pay off .

Yes @SeatTime it was a nightmare for both of us at the time, I just cant seem to get a break with them, my old setup was pulling more amps continuously than these motors but its the hard reverses which is killing it I think but I am really just not sure, I have given up lol

Thanks dude I forgot to answer @wannabeaflyer2. I did put mine on the pot but I moved it to be connected directly to the arduino pins. I have not had much chance to check what difference that made because my MM's are crap lol