On Wednesday, 6 June 2018 12:18:43 BST Ralph Corderoy wrote: > A couple more things from last night. > > In 1942, silver was available when copper was in short supply so > $1,000,000,000, in 1942's terms, was used to build a centrifuge. They > went to some effort to retrieve every scrap afterwards; detail is on > Wikipedia.
Also, we discussed a couple of other topics on our side of the table: URL Fitering: How to filter URLs using a firewall running on a Raspberry Pi that happens to be also running the webserver. (This is the Android "This WiFI Access point has no Internet access" problem again, which morphs every time Google bring out a new version of Android). Paul talked me through it and provided a couple of links: https://duckduckgo.com/?q=url+filtering+raspberry+pi&t=canonical&ia=web https://computers.tutsplus.com/articles/installing-openwrt-on-a-raspberry-pi-as-a-new-home-firewall--mac-55984 and - squidguard on pi: http://danscourses.com/turn-a-raspberry-pi-into-a-web-filter-proxy-with-squidguard/ Pros and Cons of I2C and 1-wire Interfaces: This is to communicate with multiple devices connected to a Raspberry Pi. Two fundamental elements are relevant. I2C (literally Inter-Integrated Circuit) is only good for short distances, but has the advantage of allowing addressing as part of the protocol and sensor design. 1-Wire has longer range, but the devices arrive with their unique identifier hard coded into them by the manufacturer. After last night, I was unsure whether we would be able to implement a level sensor with 1-wire capability, since they tend to be very expensive and aimed at specific industries and therefore expensive. Our current level sensors are using hall-effect devices with a bit per level, so we clearly want to multiplex that data into a serial bus of some kind. This appears fairly easy with I2C, but not so easy (because of the unique ID requirement) with 1-wire. The jury's still out. -- Terry Coles -- Next meeting: Bournemouth, Tuesday, 2018-07-03 20:00 Meets, Mailing list, IRC, LinkedIn, ... http://dorset.lug.org.uk/ New thread: mailto:[email protected] / CHECK IF YOU'RE REPLYING Reporting bugs well: http://goo.gl/4Xue / TO THE LIST OR THE AUTHOR
