Time for a new project

March 21st, 2010

While i’ve been tinkering with many things over the time since my last post.  Most of it has not really been very noteworthy or at least nothing that would probably be of interest or use to anyone else.

However, inspired by now owning a 2L turbo sports car and some recent participation in some motorsport events i’ve decided to build a racing simulator.  It’s nothing new, i don’t claim it to be but i’ve decided to collaborate some of the things i have done in hope that it might help someone else going down the same path.

The aim of this project is to produce a somewhat life-like simulator without using a standard shop bought wheel/pedal set.  I’ts not going to be real, i know, but here’s my ‘requirements’:

  • Realistic steering wheel with as much rotation as possible
  • Analogue Clutch
  • ‘H’ pattern gear shifting
  • Analogue Hand/E brake
  • Force measured brake (not movement like normal pedal sets)
  • Small/Storable/Disassembleable  (I don’t have a spare room for a sim cockpit)
  • Strong/Durable
  • Cheap!

The intended target platform is a PC running ‘Live for speed’

I started this project a couple of months back, starting with the wheel and now i have just completed the pedals.   The steering mechanism was construced utilising a 2:1 ratio cam belt driven gearbox giving a theoretical ‘lock to lock’ of 540 Deg.  A little less than i wanted but it works ok.  There’s nothing too technical about it other than the gear reduction.  It uses a real sports steering wheel too.  A keen eye might also be able to tell what the bearing/shaft supports are recycled from :)

The pedals were heavily based on the design of the commercial product from http://www.cannonsimulationtechnologies.com. Todd of CST also sells a ‘DIY’ guide for making a pedal set that is somewhat comparable to his commercial product for only US$12.  I probably could have constructed my pedals without the need for the guide but i went and bought it anyway.  I saw it like paying royalties for his design and i think it’s only fair he gets some reward for his efforts.

The main difference with my pedals are basically the fact that i have constructed them almost entirely of things i had at home already or i could acquire for free.  The problem for someone attempting to replicate what i have done is, not everyone would have the stuff lying around like i do but parts can easily be substituted.

So far, the build has only cost me about $80.  The bulk of that cost is for the rod ends that go to the tops of the pedals at ~$16ea.  The springs were about $7 each.  The steering mechanism has been totally free so far.

All these mechanics are no good without some way to interface them with a PC.  I tinkered with the idea of using an optical mouse to track an encoder mounted to the steering wheel at first but this was not far from epic fail.  It worked but was too unreliable, lost it’s center and basically sucked.  One advantage it did have was an almost unlimited number of rotations.  Pity it sucked everywhere else.  Abandoning the optical mouse idea, i moved to the old pot style joystick.  I happened to have an old E-Sky USB trainer in the cupboard that i never use anymore so i gutted that –  The result is the ability to have 4 axis analogue joystick control.  Only problem was that ideally i needed 5 analogue inputs but it was enough for ‘proof of concept’ for now.

Not long after destroying the USB trainer I came across Leo Bodnar’s site.  He sells a generic USB interface that provides 6+ Analogue inputs as well as 32 odd buttons.  While his product is good, it did not really follow the rule of cheap.  At about $80 to get one to my door, it would have doubled the current cost of the build.  Some more googling turned up a ‘product’ called Mjoy by Mindaugas Milasauskas.  It’s a DIY USB joystick interface based on an Atmega8 AVR. It seems that his legacy goes on but for some reason his website is gone.  I am making  Mindaugas’ and version of the joystick interface (for a fraction of the cost of Leo’s).  All of my designs and ideas will be published here.

The interesting thing with the CST pedals is the use of a load sensor for the brake sensing.  This is a superb idea (Although Todd admits it was not his).  This will give a much more real feel to the brake pedal.  I managed to salvage a load sensor from some industrial scales some time back – I knew it would be good for something! The problem is the interface between the load sensor and the joystick controller.  The load sensor only puts out ~2mv at full load, we need 0-5v scale for the joystick interface.  Some more googling dug up an ‘off the shelf’ chip designed for this exact task.  It’s an INA122 by Burr-Brown (owned by Texas instruments i believe).  As it turns out,  this appears to be the chip Leo uses in his controller with load cell interface.  The difference with me is, i’m going to give you all the info you need to get it running with Mindaugas’ design for free.

Details to come….

DIY PCB Boards – Toner transfer method

March 21st, 2009

I know this is nothing new,  the toner transfer method has been around for years.  One of the pioneers was probably Thomas Gootee.  He discovered the miracle of the Staples paper and described the method of making a board really well.

While i don’t want to undermine what beautiful work he has done  (in fact, if you have come here without seeing his page first, i strongly reccomend you follow the link above before going further here) I would like to document some of my experiences using this method and what i use to produce repeatable results.

Primarily, the problem for us Aussies is that the staples paper is simply not available here.  I have gone through several brands of paper and just could not find any that released well enough.  Most of the papers coating also got stuck to the board and was hard to almost impossible to remove without damaging the toner.  I have used generic papers such as OfficeWorks brand, Avery, Canon and Kodak papers.  None of which produced good results.  All were cheap and only 15x10cm papers so fortunately it has not cost me a mint in research but the one i have settled on with PERFECT results is:

HP Everyday photo paper

The item number of the papers i have (in 10X15cm) is Q5441A.  This is plenty big enough for all my projects.  It releases PERFECTLY with no residue, even on the toner.  I only soak for about 5 mins in hot water and it simply slides off.  If some is left behind, soak for a little more and it will all come off – NO scrubbing with toothbrush, heavy rubbing etc.  it just glides off the board.  I was absolutely amazed at how well this paper worked compared to all the others i have tried.  There is simply no better paper in Australia.  To make things even better – the pack of 100 sheets only cost me $6!!  that’s right, the paper is so cheap it’s not funny.  Compare that to press ‘n’ peel or other commercial toner transfer paper which is not any better and WELL above that price.

That is not the only key to this system working consistantly, the other important factor is how the toner is transferred with heat and pressure.  Irons can and do work ok but repaeatable results are hard to achieve with them.  I generally found that i eneded up applying too much heat and/or the paper tended to slide and smudge the toner which meant starting again.  The answer to this is to use a laminator but even still, not just any laminator.  90% (if not more) of laminators heat, then squeeze the laminator pocket.  They do this by having 2 heat plates before the rollers to warm it up and the rollers then squeeze it all together.  What i have found is that the heat and pressure need to be applied at the SAME TIME for it to work well.

The key here is, find a laminator that utilizes a heater INSIDE the roller.  AFAIK, the only company that produces this type of laminator is GBC and even not all of thiers work like this.  I can confirm however that the GBC ‘Creative Laminator’ available at K-Mart DOES.  I believe this is also the same as the one available from Dick Smith stores and even Australia Post.  K-Mart is the cheapest however, i paid just under $40 for mine from there.

The method of using the laminator is pretty straightforward but there are some points that should be observed:

1, Make sure the laminators ‘ready’ light is on.  It takes about 5 mins to heat up…
2, Run the board through the laminator with a piece of ordinary blank paper over the copper to pre-heat the board.  The piece of paper is important as i have found that the toner does not stick as well if you don’t.  I presume this has something to do with the rubber rollers possibly having some oil residue on them.  It could go away after time.
3, Once the board is preheated, attach your PCB design and carefully feed the two through the laminator at least two, probably 3 times
4, Dunk board and paper in hot water and leave for about 5 mins then peel slowly. 
5, Etch as normal with your favourite echant
6, Clean toner off with Acetone 

So far using this combination of the HP paper and the GBC laminator i can consistantly produce boards with tracks at 0.4mm and even less between tracks/pads.  it’s possible that it could go less but i have not tried.

Below is some pics of a board i have just done… This is for a pic based li-po monitor i found over at http://www.plmsdevelopments.com (look for the link right down the end of the text about Martin’s Electic RC exploits).

I am using a HP Laserjet 1320 with density set to 5 (maximum).  I still get some pitting in the toner as you can see in the pics but it is not evident in the final product.  I’m hoping to find a better printer that can pile up the toner – something like a HP Laserjet 4 but they are hard to find in good enough condition on the cheap.

UPDATE: I’ve since slightly changed the way i do this.  One thing is that i now tend to print my PCB’s using a very dark blue (on a colour laser)  rather than black.  It could really be any colour i spose but my theory is the darker it is, the more toner is used.  I have found this to be the best way to avoid pitts in the copper after etching as it fills all the gaps.

The problem with this is, the colour toner tends to be a little harder to melt in the laminator. Basically, it doesn’t.  It’s very hard to get it to bond.  However, Ahmad Tabbouch has written an excellent guide on bumping up the temp on the GBC laminator, as well as another mod that should help it last a bit longer.  I won’t re-hash what he has done, but here’s a link to the guide on his site – http://www.ultrakeet.com.au/index.php?id=article&name=superfuser.  Even if you don’t use colour toner, it’s still a great mod.  No pre-warming the PCB and you only need to feed it once! Highly reccomended mod, you could even substitute the resistor with a trimpot and have variable temp if you ever need to use the laminator for it’s actual intended purpose.  However, the outer shell will get a little deformed from the extra heat and i would not reccomend leaving it on for more than is needed for a few boards. 

Why you shouldn’t buy batteries from Ebay…

February 16th, 2009

So i bought the drifter and i bought a couple of 7.2v packs from the LHS for about $40 each – they were 3600mah batteries.  Good but expensive (for a cheap drifter anyway).  So, i spotted an ebay store based in Hong Kong that was selling 2 X 3800mah Ni-Mh packs at about AU$40 for the two posted.  It seemed like a pretty good deal so i thought what the hell.  I mean, it’s not as if i need special ‘super power’ racing packs anyway as the car is not raced as such.

I buy items from HK all the time so i had no hesitation.  My Heli’s, parts and most of my Maxx parts all come from HK and i have never had any problems with the service.  Infact, i’ve had more problems with local sellers on ebay than i have with international ones…

Anyway, 7 odd days later I got the two packs in the mail.  Generally the first charge should be for 10+ hrs at 1/10C or 380ma in this case.  I done that, the packs got warm as they should and nothing more.  So, i popped one in the car and went for a drift.  It seemed ok but didn’t last very long – about 5 mins which is pitiful.  The other pack was the same.  So, i slow charged them both again and gave it another shot the next day – Same result.  I have never experienced this type of problem with battery packs so i messaged the seller with a general question of ‘How many cycles should these batteries need to achieve full capacity’.  They replied with a generic text along the lines of ‘make sure you charge for 10hrs before use’.  I was not overly happy with the reply but i thought i’d just stick with them for a bit and see what happens.  After about 10 cycles and now using my smart charger at 1c rate (3.8A charge), the batteries would still only take about 1200mah.

I went to message the seller again but it seems that they are ‘no longer a registered user’.  Odd since they had been a member since 2004.  At about the same time I happened to notice that the 3800’s seemed to be much lighter than my 3600’s.  I was starting to suspect that perhaps they were not 3800 cells.  So, with the seller no longer active, beyond 60 days for buyer protection and the cost of a return likely to be at least half the cost of a new battery i decided to crack the heatshrink on the pack to inspect the cells.

When i finally cut through the two layers of shrink wrap i expected to see something dodgey but nothing prepared me for this!

battery_assembled1
battery_opened

That’s right, NO WHERE NEAR 3800mah at 1300mah and not only that they are Ni-CD cells, not Ni-Mh!!!  Buyer beware!  This could have caused huge problems.  I was charging this battery at 1C (3.8A) when it is not really supposed to be charged at any more than 1.3A.  If this had caused a fire or explosion I could have been in serious trouble.  Not only that, it’s complete fraud. I’m not really sure how you could avoid getting these dodgey packs other than staying away from these generic ones completeley.  My guess is that most of the cheapies on ebay are probably all from the same factory and just labelled differently.  Either that or get a 100% money back guaruntee that the packs you are buying are definately of the specified capacity and chemistry.  

If the seller resumes business then i will supply thier ID to anyone who wants it, otherwise just be very careful.

Another toy

February 12th, 2009

Over the xmas break i decided to invest in another RC toy.  I love my t-maxx truck but it’s noisy, messy and generally costs a lot to keep it running.  So, i thought i might have a go at an electric car and one step more – a drifter.  I managed to pick up a brand new Tamiya TT-01 chassis off ebay for about $100.  Throw in an ESC, steering servo, RX and a battery and you have a running car.  After that just bolt on some drift wheels and you’re up and drifting.

The advantage i saw with drifing is it’s low speed.  Low speed = less damage when you hit something = cheaper to run.  The other advantage is that you can drift with a real stock crapper, there is no need to do untold amount of upgrades to get it to drift well.  The stock Mabuchi 540 motor does the job fine and there is not a lot of advantage in going for more speed.  Drifting needs torque and not speed – I’ts more about driver skill than how many $$ the person has spent on the car. There are some minor upgrades that come in handy however, notably the shock absorbers.  On the stock TT-01 they are just friction types.  I swapped these for some oil filled dampeners and this has made a significant improvement to drifting.  You also really need to lock both front and rear diffs (nothing a bit of knead-it can’t handle)

Unfortunately the drift scene seems to have almost depleted totally from what it used to be at Hobby Habit here in South Australia.  I remember going to a ‘drift night’ there a couple of years back and there was probably about 30 cars.  It was awesome.  Now, unfortunately there are only about 5 compeditors in the drifing and the drift meet is now only part of thier friday night Hyper10 Racing as a time based event wich is somewhat pointless for a drifing comp.  It’s still great to go there in practice time for some fun though.

Tim and I went there a few times and it was soon apparent to Tim that he needed one too so he bought one not long after i did.  It’s very challenging but even more fun….

If anyone in the southern adelaide suburbs is interested in getting into drifting and/or would like to meet up for some drifting, post a comment here

Anemometer update

February 12th, 2009

It’s been a while since i posted the original concept of the anemometer and much more development went into it after that.

I have now made a propper PCB and gone to a 20X4 LCD as well as probably tripling the lines of code.

The code now displays a speed for every revolution of the vane. It’s a little hard to read in windy conditions so i also added an average reading which is an average of the last 10 readings.  I also added a feature into the code to output the average value via a serial port on the chip. The serial port data is pumped into a MOXA nPort server, which is mapped to a virtual serial port on my server over the internet (some kilometers away).  The data is logged via a PHP script, further averaged and pumped into an rrdtool database at regular intervals.  This gives me the ability to easliy see what the conditions are like from anywhere in the world.  It’s geeky i know, and it was more of a ‘because i can’ feature rather than a requirement.

Feel free to check it out – http://www.hux.net.au/anemometer It’s basic but does the job.

anemometer_mounted

Action!

November 11th, 2008

I took the boat out again last weekend and we did some more tinkering to get more speed.  The trim tabs did not improve performance, they hindered if anything so I pulled them off the boat.

It was flowing nicely, the copper pipe helped with the heat in the coupler but i’m going to change it for something a little smaller to get more surface area contacting the header pipe.

The level in the pond is getting really low now, too many shallow spots etc.  It’s probably time to either find another spot or possibly shelve it for now.  Might still see maybe one more installment but i think i’ll end up waiting for some more rain to fill the pond rather than going back to the salty river.  Time will tell.

 

Octura Coupling still not quite good enough

October 23rd, 2008

So we took the boat back down the pond for another shot.  It went superb!  I would have to say that it was the fastest it has run yet.  With no real problems causing us to take it home it gave us the opportunity to give it a bit of a tune and get some more speed out of it.  The latest video shows it going significantly faster and now on 98 octane fuel and a different plug there is no missfire.  It was truly singing!

The water level was getting a bit low in the pond now uncovering 2 ‘islands’ in the middle.  It proved to be a little hard to negotiate between them so i stayed in the bigger area.  It looks like i’m just doing circles but infact the back run is quite straight.

The boat flipped a couple of times, the last one got caught on video but the first one was much more spectacular.  The boat held up well tho and once the water was out of the engine it started fine.

So, on to the coupler.  Well, i would say that it’s still the best solution so far but it’s still not quite up to the task.  After a full tank of juice (first time!) it was a bit melted. The problem is that most gas powered boats have water cooling the exhaust header so any product that i get is likely to only take 200 deg or so.  Mine does not have any cooling at the moment.  So, what i have decided to do is wrap some 1/4″ copper pipe around the header about 4 times.  I am going to run cooling water through it from the rudder and see what that does.  Hopefully this will help reduce the temp of the pipe and therefore preserve the coupling.

I have also got some stainless sheet to put on the back of the boat as trim tabs to help get it out the water a bit better.

I’m working on trying to get an onboard cam going too :)

Quick update

October 16th, 2008

With the leg now complete, i moved back to the exhaust.  This has been a problematic area from day 1.  The problem is associated with the poor balance and vibration in the motor.  Basically, the exhaust is shaking itself to death…

 

Originally it was solid all the way through but the thinner stainless of the pipe fatigued and cracked from vibration.  So, in the last run i tried a silicone coupling i got from rcboatbitz but it only lasted the previous run before splitting and that’s what caused the boat to stall at the end.  It was not really good for the job as it is designed for much smaller pipe and it was stretched to go over the 1″ pipe of my setup.

I’ve now just fitted a product that is made by octura.  This one is still silicone but it’s reinforced with 4 layers of fibre as well.  This one was 7/8″ so it’s still a slight strech over the pipe but not as bad as the other one.  I have since found that octura do the same part in 1″ as well so if this one splits i’ll order one of them.

The bigest problem is the heat – it’s classed as a ‘high temp’ coupler but i have no idea on the actual rating of it.  I tried to find some specs via the oracle that we know as google but it turned up nothing so far. With any luck it will actually hold up…

 

Skeg/Leg redesign

October 15th, 2008

So after the last run I saw the need to redesign the bush/bearing setup in the leg.  the original design simply used 2 collars of teflon around the shaft.  After visiting a few sites and seeing how some other ‘DIY’ designs were done i settled on one developed by the guys over at Oxford County based on some K&S brass tubing.

The outside is 5/16″ and the inner is 9/32″.  The 1/4″  shaft perfectly slides inside the 9/32 and that slides perfectly inside the 5/16 tube.  The smaller of the 2 tubes is cross drilled to allow for lubrication between the shaft and larger tube.

The bearing holder is a little bigger as well as now going for a stainless ferrule.  No real advantage here but the only reason i went for brass on the original one is because the tradition is to solder the flex shaft in.  Instead, i ended up using Loctite shaft lock.  This is super strong stuff and never even hinted at breaking loose uner the torque of the ryobi.  So, to keep it looking nice this time, i used stainless.  Also, this time i have used a roll pin to atttach it to the shaft rather than grub screws (which were a little problematic last time).

Almost ready to rock…

Another run with the boat

October 11th, 2008

I’ve been getting all my RC toys back in working order over the last couple of weeks.  One being my Traxxas T-Maxx monster truck and the other is the boat.  I sorta stripped the radio from the Maxx to put in the boat so i got another RX and a couple of servo’s to get the maxx running again.

The boat also needed a new radio box and some other minor repairs.  With a little work and some help from Tim, i got it back up and running.  I also found a new/better site to run the boat.  It’s the old (now abandoned) Lakeside Leisure park site.  There’s a nice little pond in the middle to run the boat on.  It has a couple of downsides like limited access to the bank and a shallow spot in the middle but the huge plus of it being FRESH water and not salty onkaparinga river water far outweighs them.  It’s not all festy and stagnant either like one might suspect.

I’m not 100% sure on the legalities of using the pond since it is infact private land but there are no signs up telling me to stay away and i did not even have to jump a fence or anything- just walk straight in.  Not only that, other locals seem to be using it extensively for riding motorbikes on. I don’t think i’m going to have too much to worry about.  That is, until the land gets sold off and subdivided as the land is for sale…

So, we got the boat in the water and even remebered the camera this time!  There’s a couple of problems with it after the run.  Mainly the fact that the rubber/silicone header -> pipe joiner split which caused it to stall (no back pressure).  I’m going to have to find something else to do the job. The engine also seems to either detonate or misfire every now and then – you can hear it in the video.  I think with 98 octane fuel and a bit more oil it should go away tho.  I’ve also made up a stand for it now.  Makes transport and use so much easier.

I’ve also now decided to make up a new skeg.  The current one is not ideal, it uses teflon as the bearing and wears too quickly.  I’m changing it to use brass and to have more bulk. More on that later.

In the mean time, enjoy the vid…