I was able to set up the full experiment with my Home Education Computing group yesterday. We had got hold of some Copper Sulphate from ebay and stopped filming the snow.
We planned to film one form set of crystals from above using the Visual-Pi-ser as a stand and the other from below lit from the top.
To film from underneath a stand was made from a cardboard tube and a slit cut to allow the camera to be placed underneath. this would also double as a lightbox for other projects with the addition of some greaseproof paper (to diffuse the light) and a petri dish.
This camera also needed the focus changing a it was significantly closer to the subject than the standard minimum distance of around 47cm.
So the craft knife was called for again and the glue blobs cut off another camera (this part of the process seemed to really enthrall the boy and had them really excited about the idea of 'hacking' hardware. The process used to change the focus was described more fully in the Visual-Pi-ser side project blog but essentially you need to cut through the glue blobs to free up the lens on the camera board. You do need to be careful not to damage the delicate board whilst doing this so take care. Once this is done you can focus the camera by turning the lens
Before making the solutions we did the science bit of the learning talking about solutions, solutes and solvents. We talked about how things Dissolve and about how we might separate a mixture and a solution. I was really pleased at the boys recall and understanding of things we had talked about before. I even used a whiteboard substitute to do a bit of diagramming so they could visualise the process of the copper Sulphate and water forming a solution.
Before we moved onto making the solution we covered the safety aspects of using chemicals in experiments (if you are trying this at home please look at the specific safety information from CLEAPS and follow the advised precautions). We talked about the specific risks fro this experiment and what we could do to protect ourselves. This caused some excitement and delay as Toby decided that the goggles (from his Science set) could not be used by anyone else. Once we had negotiated terms for the sharing of safety equipment we were able to move on to making the solution.
To get the best results for crystal formation it is important to use a saturated solution. This means that there is as much solute in the solvent as it can dissolve. To make the saturated solution we added hot water to the Copper Sulphate powder and the boys took turns stirring. We added more powder and stirred vigorously until no more would dissolve in the water. You can see this point when even after repeated stirring the solute is dropping out of solution. If the solution is not saturated the process takes longer and the crystals are not as impressive so it is worth time and effort at this stage to ensure the solution is as saturated as possible.
Once we had a solution ready (or poisonous potion as Jacob later described what we had been doing) we set up the RPi to take the pictures.
We talked about jpw long the process would take and how long we should leave it between pictures to get the best results. After the earlier experiments we did the decision was taken to take pictures every minute. We also decided to use the timelapse method I had used for the snow pictures (Scheduling a BASH file using cron) rather than the timelapse mode of the Raspistill command.
The file was already set up on the RPi that came with the kit (after being used for the snow) but it needed replicating on the second RPi so Jacob set up the scripts with a little help from Toby and myself. This was the first time he had really used the RPi so he was really excited to be controlling the computer using the command line (a big change from his iPad).
The code we used was as shown below:
#!/bin/bash
DATE=$(date +"%Y-%m-%d_%H%M")
raspistill -o /home/pi/camera/$DATE.jpg
To set the cron job we used:
Sudo crontab -e
and the schedule line:
* * * * * /home/pi/timelapse.sh 2>&1
With the RPi set up they were moved to the sideboard (to keep the copper solution out of the reach of our 2 year old). This move was the main reason we had decided to use the scheduling and file method as it meant we could set it all up on the table and move the kit then just plug it in and it woul dsit and take pictures without the need for a keyboard or monitor to set things off. We also made sure the RPi both had WiFi adapters up and runing before they were set up so we could connect via SSH or VNC and check on the results.
With this done the Copper Sulphate solution was added to to petri dishes (whilst wearing goggles of course) and placed in the set up.
Now all that remained was to wait and see what happened.
After quite a short time (around an hour) some results were visible and crystals started to be visible to the eye. The RPi were working well and pictures being taken so all was good.
In the evening we got impatient and seeing some large crystals formed we downloaded some of the pictures and put together a couple of timelapse videos to see the results.
I hadn't had time to experiment with other software so we used Window Movie Maker Live again. This time with no trouble but there were less pictures to process.
The reults of the top view camera were quite good clearly showing the crystals forming over time. I think the focus might be a little out so we may try doing this again with a slightly adjusted camera.
The experiment short from below worked really well and produced a really nice clear picture. The view with back lighting really shows the crystals nicely and the process of them forming is really clear from the video. The crystals are also a little magnified as a result of being so close to the camera and the adjustments made to the lens so it looks a little like viewing it through a microscope.
The best thing about the results is that these were shot with very basic equipment by two Home Educated students 6 and 7 years old. I am very proud of what the boys have done (with a little help and guidance) and they were really pleased to see the results. My school students will have a lot to live up to when I am well enough to return to work and run the School version.
We have left the experiment running so we may also be able to extend the length of the videos a little i will post the results here if we do. We may not get to that however as the boys are determined they want to grow a big crystal using one of these crystals as a seed so we might see if we can do that and film that instead.
