Apr 102016
 

Ok, so remote means just a few meters away, either in the house or in the car. Somewhere warm anyway.

So, as mentioned in my previous post, I’d done a lot of research, and one of the things I came across was this video:

This is what I want to be able to do. I’ll never have the room for an actual observatory like this one, but I could at least automate a lot of the work. That’ll scratch at least two, maybe three, of my geek itches. Of course, everything has to be Linux based, and also as cheap as possible. With that, I decided on at least the following to start with:

  • AstroEQ – Definitely needed goto support on my EQ5 mount to start with.Fully made systems can be bought (minus steppers and mounting hardware), but I already had most of the parts laying around the place so decided to make it myself using an Arduino Mega
  • Indilib – This, running on a raspberry pi acts as a remote control server for anything that I wanted to add. All devices had to be supported, or easy enough for me to add with my limited programming skills.
  • Guide Scope – These are used to ‘lock’ onto a star and make sure that the telescope mount follows it precisely. Long exposures of up to even 30 minutes can then be achieved without too much difficulty. Initial plans are to try and use the Raspberry Pi camera (will try both standard and NoIR) versions.
  • Focuser – Last essential part for remote control is the ability to focus the telescope. This will use the DSLR attached and a stepper motor coupled to the focus knob. There are a couple of arduino based projects that emulate the MoonLite protocol, which is supported by indilib.

Once I’m happy with this lot (and I *will* blog my progress) and have some of my other projects finished (*cough* R2), then I want to take a look at a couple of other add ons such as:

  • Filter wheels – I can use kstars to take many photos with different filters in place, and also with a black filter I can automatically take dark frames for stacking images. (Dark frames are used to remove noise in the picture that is generated by the DSLR)
  • Auto lens cap – A simple servo driver to cover the telescope main lens. Not really necessary, but figured it would be a nice project.

I should be able to do all of this fairly easily. I already have most of the components necessary, and the software running on my workbench. One of the big issues I’ll need to work on is just how to mount it all to the scope and stop the cables getting tangled!

My next blog should be on building and configuring the AstroEQ.

Apr 052016
 

Hi, my name is Darren and I’m a serial hobbiest.

Well maybe not that bad, most of my hobbies are pretty much related (electronics, computers, science), and a lot are things I’ve been interested in since I was a kid. Most recently, I’ve invested in a fairly decent telescope and mount to do some visual astronomy, but more for astrophotography. I want to take pretty pictures of things very far away! So after a lot of reading of various blogs and websites (Star Gazers Lounge forum is fantastic), and watching numerous youtube videos, I got a tripod for my camera and a couple of cheap lenses off eBay. That is all that is needed and you can get some half decent shots.

My astrophotography album

But it wasn’t enough. So I dove back into the forums and did even more research, and learnt a few important things.

  • Telescope – Numerous different types, mainly split into reflectors, refractors, and catadioptric. All have their benefits and downsides, but for doing astrophotography the telescope isn’t the most important item surprisingly.
  • Mount – This, for astrophotography, is the most important thing to get right.You need to have a solid mount for doing anything more than a few seconds exposure, and one with tracking in Right Ascension at least, to track the stars. And it really needs to be an equatorial mount to avoid rotation of the starfield as it rotates.
  • Eyepieces – You need eye pieces to view through a telescope, and the shorter the focal length, the greater the magnification. These are generally only used for visual astronomy, as cameras bypass the need.
  • Camera – Most DSLR cameras block out a large part of the infra red by design, but you can get them modified to remove this filter and get much more vibrant images. Its not a necessity, but definitely a nice to have.

Whilst learning all this, I had a thought in my head about some form of computer control (Linux based, of course) and actually stumbled upon a few projects to help with this. The first was AstroEQ which was an opensource ‘Goto’ system (select a star, and the telescope will automatically move to center on it) designed around an arduino. That was a perfect start for me, and I was pretty sure I could get it working from Linux. Thats when I discovered indilib!

Indilib is an open source system for controlling all sorts of astronomical instrumentation, not just goto mounts, but also things like auto focusers, digital camera, filter wheels, and other custom devices you may want. Even better, all this can be run from a Raspberry Pi as the control server and a laptop using the actual astronomy software. This would mean I could set it all up, and retreat to somewhere a little warmer to actually do my observations and photography. I’m sure this is against the amateur astronomers code or something, but damn it gets cold out there.

Along with indilib, there is kstars. This is a planetarium program written for the K Desktop Environment, and with EKOS plugin can control any indilib hardware. Not only that, it can schedule work and sequences, and help you plan your observations.

I’m going to (try to) write more blog posts chronicling my progress on getting all this set up, and some HowTo posts on using indilib on a raspberry pi, with kstars, and any custom hardware I make.

Mar 262016
 

It seems that xmas and new year is when all the part runs start. At least that is what it feels like to me, for all the parts I want.There has been a sudden rush in ordering things for R2 which means I nearly have everything I need to get him put together and mobile. The one part I’m still missing is the outer ankles, which I am hoping will be on a run soon. The last few cosmetic pieces I need are due soon too, such as utility arms and LDP. Progress whilst waiting for these parts has not been too bad, but I do keep coming across problems to work around. I guess that is the fun part tho.

On the electronics front, I managed to (I think) blow up my amplifier. I still need to hook it all up again and test it. I’ve a feeling that the switch I’ve got for main power isn’t rated high enough for the current that is going through. I’ve also decided to change the layout of everything, and install an actual touch screen inside R2 for the Raspberry Pi. This will give me the ability to control certain aspects of the software, and also at a pinch I can plug a usb keyboard and mouse in to do onsite programming whilst away at a convention or such like. I’m also currently waiting a Raspberry Pi v3 which will give R2’s brain a bit of a boost. Overall design hasn’t changed much, it’ll still all be controlled via i2c, but will also have wifi and 3g internet connectivity, turning R2 into a wireless hotspot! I will have to see how much the aluminium body affects the signal, but can always put an external antenna somewhere.

IMG_0298_CR2_embeddedI have more or less got the legs finished, and have done a test fit! Must say, they are looking rather good. All the parts slot nicely together and are pretty solid. Of course, I still have the problem of a lot of the screws and bolts being imperial (We’re part of the rebel alliance, don’t want any of that imperial rubbish!) rather than metric, so getting hold of replacements can be tough. This is more of a problem seeing as I’ve had some of these parts for quite a while and not only been moved around the office in the old house, but have moved to the new house and gone in and out of the garage, so some of the fastenings have been misplaced along the way.

I also decided to get one of the nice new hydro formed domes that are available. I was never too keen on the existing one that I had, and the new domes come with the mounting ring to fasten it to the body which meant one less thing I had to fabricate. A lot of the tutorials on the forums are geared around these domes too. Not only did I get a new dome, but I figured whilst I was doing that, I’d also upgrade all the things to go in the dome. This meant getting the ultimate hinges, aluminium holoprojectors, aluminium logic surrounds, aluminium eye, and even the fancy PSI holders. All this together gives me a pretty much top of the range dome for R2. It also means I can do a quick and dirty rebuild of the old dome at some point and create a different astromech.

IMG_0304_CR2_embedded IMG_0309_CR2_embedded IMG_0489_CR2_embedded
Which brings me more or less up to date. The dome is nearly finished, I just need to put a few final touches to it and tidy up the cabling inside. I even got the dome servos all hooked up and took a short video. I need to replace the arms on the servos with something a bit longer to get a bit more throw on them, but overall I’m pretty pleased.

Next step is to get to work on the body. I’ve got some of the ultimate hinges and have some installed already. Just need to fit the servos to them. I also need to trim down my data panel to fit it into the breadpan, but that shouldn’t be too much trouble. The one part I’m having issues with is the charge bay breadpan, it just doesn’t want to fit in properly. I may have to resort to some pretty hefty modifications on it.

 

 

I’ve given myself a deadline of June to get him mobile, but that depends on when part runs happen. Fingers crossed the outer ankle run starts soon.

Dec 042015
 

11934535_10156061505195316_3190924556943319116_oIts been a long time since an update, but we moved house at the start of the year and things have been hectic. At least, thats my excuse and I’m sticking to it! I have been making progress with R2 in the last couple of months, doing a lot of work on his brain for starters, and painting various parts.

Code wise, there has been a couple of fairly drastic rewrites since my last update. The interface is a REST API, which sends commands to various modules as before. I’ve added a scripting module now, so that scripts or loops can be initiated such as random sounds, or a dance routine. The servo module had to have a major rewrite too as I discovered that I could only control one servo at once and had to wait for that to finish before another command could be sent. That wasn’t much good! I’ve also written the first of the actual controller interfaces (not counting a simple web one for testing), R2 can now be controlled from a PS3 controller. Button combos are read in from a csv file to trigger certain effects or scripts. Lastly, R2 now has a voice, and can play any mp3 stored in a directory, including selecting random ones from a list of types. Next step is to get either the Pi or the A la mode Arduino to control the speed controllers. I don’t want to run them off the Adafruit i2c servo controller for safety, I’d rather drive them directly and have some form of watchdog to make sure R2 doesn’t go on a rampage. All the code is still available on GitHub under my user, dpoulson

The PDU also needed a rethink, not least of all because of the amount of current it needed. The setup now has feeds directly to the speed controllers, with relays on the output from them to the motors so I can break the circuit if needs be. These relays will automatically turn off if the battery is disconnected so that any pushing of R2 will not feedback into the speed controllers and fry them. The relays will also be controlled from GPIO pins on the Raspberry Pi so I can disconnect them via an API call. I’ll also have an input for a kill switch that will have to be permanently on if any of the motors are to be powered, possibly using a transmitter in a replica droid caller or hilt of a light saber. I’ve a base idea for the new relay controls:

Powerswitch The relays I’ve found are Omron G4A-1EA, which have the benefit of the switched load being on spade connectors on the top, rather than through PCB traces, which when I did the calculations would need to be massive to support the potential current running through them. This allows me to make a simple PCB with the controller circuit, and hook the 24V battery up to it to power the coils. If the battery is removed, the coils turn off and the circuits are broken. No fried speed controllers.

The 24V connection will probably go through the fuse box I’ve installed, with a hefty fuse. The makers of the speed controllers don’t actually recommend a fuse but I’ve seen a few comments saying a 60+A fuse can’t be a bad idea, just in case!

The battery will connect directly to the center contacts of a DPDT switch, with the fuse box on one side, and the charger connection on the other. This will allow charging the batteries without taking them out of the droid. Not sure if this is best practice or not, needs more research. Currently they are just a pair of 12V SLA batteries that I had, connected in series to give the full 24V.

I’m hoping to get some time either this weekend or next, to hook up the motors, speed controllers, and battery, to test them out and get an idea of potential current draw. They’ll be controlled with a standard RC transmitter/receiver for now. If I can get the legs onto R2 he may even be drivable by xmas.

Fingers crossed!

Sep 162014
 
Replicator

SG-1 Replicator

I’ve been wanting to give resin casting a try for quite a while now, and decided to start with something fairly simple that I’d need a lot of to get some practice in. The perfect thing was replicator blocks from Stargate SG-1. These are made from hundreds of little blocks, and a few people have these for sale on Shapeways. I ordered a few of them as originals, along with a starter moulding kit from Easy Composites. The kit is quite good, and comes with most things that you’ll need to do simple moulds. The only extra things that I ended up getting was some clay and mould release, but that was because I was going to be doing a two part mould.

This weekend's project.

Moulding and casting starter kit

It would be a waste of time going through the whole process of making moulds as there are plenty of tutorials and youtube videos on the various techniques. I just followed some of them, but I did learn a few things along the way.

Mold box built

Making a mould box

Base layer of clay ready

Base layer of clay in the box

This is the difficult part so far, making sure that the object is in place, and the seams are clean. Took a lot of work and will see how it comes out.

Pressed the blocks into the clay and made sure the edges were clean

Now just to wait for it to set, and then do the second part.

First half with the silicone poured in, waiting to set.

First part of mould done, eventually managed to dismantle the box I'd made. Note for next time, there is such a thing as too much hot glue.

First half set and deboxed

Clay removed and everything cleaned up, box remade, and second half of mould poured.

Reboxed. and second half poured.

So, first attempt didn't go too well. Did learn a lot tho. Need to come up with a better way to make the mould box (or don't use as much glue), don't make the keys too deep, more mould release when doing the second part of the mould, and make bigger pour entry points. May also join the pieces together with a sprue in the next attempt.

Right one turned out ok with a few air pockets. I ran out of resin on the left one.

With the mould done, I did my first attempt at casting. Whilst it didn’t turn out particularly well, it wasn’t the great big mess I was expecting. I hadn’t taken into account the amount of spillage when I poured into the mould, mainly due to the small entry point, so ran out of resin on the second block.

I’m going to remake the mould now, taking into account a few things that I learnt on the way, along with some tips from experts.

  • Make the mould box differently. I used acrylic and a hot glue gun which made it very hard to dismantle. I think I’ll use clay for my next one as I should have enough of it.
  • Do the base of the mould first, and press the parts into it before making the box round it. Was difficult to get in to make a clean seam.
  • Don’t make the key marks for the two moulds too deep. I did stupidly small deep holes first time, and it made it very hard to pull the mould apart, which leads to….
  • Use more release agent when pouring the second half of the mould.
  • Make the fill area bigger, and it needs vents to allow the air to come out. It has also been suggested to use an injection technique with a syringe to force the resin into the gaps.
  • Make more resin than I think. Its also hard to make small batches, so my next mould might incorporate all four blocks I got from shapeways.

If I get the next one working well enough, it’ll be a production line I think. By my calculations, I’ll need about 200 blocks to make a standard replicator. I’ve also ordered some metal powder to use in the moulds to give the finished blocks a metallic look, along with some black and dark grey pigment which will hopefully mean less painting of the finished product.