I have been really lazy and not really updating this blog very much, I have so little time as it is with my many projects on the go that the documentation side of things sort of gets left behind…
First of all if you havent’t read the first instalment of the LN2 generator then I suggest you have a quick look at this link here it explains the idea behind this sytem and also gives a bit of background as to how the system works.
I have made a few modifications to the original system schematic there were a few ideas that I had which just were not mechanically possible so these have now been revised and I thought I would share with you the issues that I have faced thus far and what I did to overcome or engineer out the problem.
Here is the new schematic, it isn’t very detailed because I am modifying and changing the system as I go depending on what issues I come across.
Well this is my first post regarding my Lister engine project!
It all started when I saw the bottles of old engine oil at the back of my place, I was wondering what useful purpose this oil could serve. After looking around on the internet I found some sites referencing babington burners etc which are simply oil burners that pre-heat the oil and oxygenate it ready for burning. This method would be great if we required a lot of heat but where I live we don’t get snow and it only gets very cold at night and even then this is mild compared to some places on Earth!
I kept searching and eventually came across some a couple of forums where people were living off grid using Lister engine generators, they were burning either straight or waste vegetable oil (SVO, WVO) in these engines and they were proving to be extremely reliable.
So in my previous post I mentioned about generating my own liquid oxygen which I will use to compress a gas cylinder up to 3000PSI!
My main reason for this is so that I could do oxy cutting with my hho torch, if you haven’t checked out my HHO torch here is the link. So there’s a few ways to get gas up to this pressure, one is to heat it, but this will leave you with a high pressure container but the same quantity of gas, compress it using mechanical means ie a compressor which would be very expensive due to the high pressures involved the third way is to cool it!
I read a very interesting article by Ben Krasnow a while back where he built his own liquid nitrogen generator using a Stirling cryocooler, this system is a reverse Stirling engine basically where by instead of inputting a temperature differential you put in mechanical motion via a linear motor and out comes a temperature differential. This unit is brilliant and he picked it up for a bargain ~300 from Ebay.
I don’t have a big use for liquid nitrogen or even liquid oxygen really, but man it would be a decent achievement to be able to build your own plant that can produce it at home, especially in some appreciable quantity. Ben’s unit can yield around 1 liter per day of LN2, which is slow but still cheaper than you can buy it for normally.
Once I came up with a purpose of having LN2 (to produce LO2) I looked at the possibility of producing my own stirling cycle cooler, looking in depth I don’t have the required metal working toolage to get remotely close to being able to produce one of these things so I came up with the idea of using a regular refrigeration compressor to do my bidding.
My theory initially involved creating a decent pressure drop across an expansion valve, this is the basic Joule Thompson expansion method used in refrigeration everywhere. Depending on the type of gas and the ratio of expansion of the gas will determine the final temperature. The lower temperature is then used to cool the incoming compressed gas and the cycle continues until the temperature reaches low enough temperature to cause condensation of nitrogen / oxygen into liquid. I have drawn the following system diagram of my idea.
In Australia we have an issue where we cannot outright purchase oxygen and acetylene bottles for home gas welding / cutting. This sucks because as a hobbyist I don’t really use a lot of gas but it is very handy to have when you need to braze some tubing or a small weld or something. In Australia you need to have an account with BOC gas or Air Liquide and pay a monthly rental fee in the order of 30+ bucks depending on the size of the bottles + an upfront fee of the gas.
The solution is to build your own Hydrogen torch setup. Hydrogen when mixed with the perfect Stoichiometric ratio which is 2 parts Hydrogen and 1 part Oxygen as generated from electrolysis will burn hotter than an acetylene flame.
These days you can purchase “dry cell” electrolyser’s for relatively cheap, this unit is a series of flat stainless plates which are used to split the hydrogen and oxygen molecules when exposed to a minimum potential differnce of 1.23 eV. The plates are sandwiched together between a gasket which electrically insulates and seals the unit. The gas produced rises to the top where it passes through holes in the plates and out the end capping, the rising gas causes a suction on the other end of the unit which creates a circulating water current that draws fresh water through the system.
The unit I have is a 43 plate unit which is capable of producing 5+ litres per minute of hydrogen and oxygen, I purchased it for $220 AUD including postage, the unit is $160USD normally. The model I have is the AU43 which I bought from here. The guy I purchased it from was very helpful and the prices of the unit I think is very reasonable compared to some of the units being sold on Ebay.
Below is a small system diagram, 12v is applied across each set of positive and negative plates, I’m not 100% sure how it the neutral plates work, but it appears the differential voltage is divided amongst the neutral plates which then also cause electrolysis, it’s a strange system but appears to work rather well and is a proven design.
Hello people, here is another relatively obscure topic that again probably won’t apply to a lot of people specifically but the process I use can be ported to any other software you like. I thought I would just share the info I have found as it has streamlined some processes for me and could help you out as well. If you get bored with the specifics skip to THE SOLUTION below.
So where I work we use a piece of software called MDT Autosave which has been recently purchased by Schneider I believe. MDT is a change management software which targets PLC and SCADA version control, basically you browse a list of PLC’s from within MDT and select the one you wish you program and MDT loads up the programming software and displays it to you ready to go.
Concept (the Modicon PLC programming software) has an internal security feature which you can use to limit the access that people have depending on their logon credentials. I log in as an Administrator which gives me full access, however we have other users on site which we only want to give ‘view only’ or only allow them ‘force’ access. So what we do is create some generic access accounts in concept that allow a user either admin, force or view only access.
So today I have been trying to figure out how to automatically retrieve forced registers inside of a Schneider Modicon Quantum PLC. A force for those of you that don’t know is when you override what the code or input is telling an address to do with a value that you want it to do, for example I might have a button connected to a PLC input which is off, I can force this address (1x address for inputs) in the PLC to an on state or vice versa. The same can happen with code, an internal address (starting with 0x) might need to be forced to do my bidding so instead of waiting for the code to enabled it I can manually change its state to whatever I need.
Schneider actually provide a ‘loadable’ which is a piece of code that can be downloaded to the PLC which will yield these results however it is a pain in the ass having to load these loadables into the PLC in the first place if they are running your critical plant, so I decided to sniff the traffic between the programming software (in this case Concept 2.6) and the simulation PLC which is simulating a quantum 534 PLC. To do this I ran an XP machine with the programming software and created a network between the host and guest machines, I then ran the PLC simulator on the host machine and connected to it from the guest machine (the XP machine running in VM). All that I had to do was send commands and sniff the data in between using Wireshark, this wasn’t the easiest as there are a lot of commands flying backwards and forwards between the PLC and simulator but I managed to decode some of them below.