Re: XO-1.75 microphone socket
In Tony's defense, he was reminding us to fix what was an acknowledged omission in XO-1 (the C3 motherboard which fixed it was never put into production). We never reflected the change in the 1.5 specs, causing further confusion. I apologize for accepting an 0402 for the current limiting resistor on 1.5 --- I requested 1206, but anything larger than an 0402 would have required quite a bit of board change (due to separate ground planes under the analog section). The spec'ed continuous rating of the 1.5 microphone input is +9V/-6V. Exceeding this is likely to damage the laptop. Yes, personally I recommend building sensors to use the internal 2V biasing supply. It uses the built-in rechargeable battery! Cheers, wad ___ Devel mailing list Devel@lists.laptop.org http://lists.laptop.org/listinfo/devel
Re: Re: Re: XO-1.75 microphone socket
Scott Thanks for your comments. As this is now more a discussion on education, I have copied to IAEP. Background for the IAEP list: Suggested experiments for using TurtleArt with external sensors are at http://wiki.sugarlabs.org/go/Activities/TurtleArt/Using_Turtle_Art_Sensors The allowable input voltage on the XO1 microphone socket is ?0.5V Why not use 1.5V alkaline cells? Alkaline cells exceed the published specifications of the XO1.5 (and can damage the XO1.0) > Or measure voltage from a lemon battery? Though quite safe, the lemon battery (0.9V) exceeds the published specifications > "measuring AC amps" example should be moved to a separate "only with > supervision and adequate care" page This generates typically 30mV, 1/300 of the safe input of the XO1.5 and is quite safe. > Maybe also the "Generating electricity" example also, although it would take a lot of turns of wire, a pretty strong magnet, and very vigorous motion to exceed 9V This generates 10?s of microvolts, a safety factor of 1,000,000 > maybe also the "burglar alarm", depending on whether the XO-1 is > always safe if its inputs are shorted My understanding is that this is safe. I do have some doubts on including information on measuring mains power. http://wiki.sugarlabs.org/go/Activities/TurtleArt/Using_Turtle_Art_Sensors#Measuring_power There is the risk that this might encourage students into unsafe areas. I was encouraged by https://docs.google.com/present/view?id=df7px97w_54fs9nh9fj (in Spanish) which suggests using a tong ammeter to measure power in mains circuits to measure carbon footprint. The TurtleArt sensor is superior, it can log over an extended period, costs about $1 and can be constructed with village technology. The tong ammeter costs about $300 and takes instantaneous readings. Tony On Tue, Nov 16, 2010 at 11:38 AM, Walter Bender wrote: > On Tue, Nov 16, 2010 at 11:19 AM, C. Scott Ananian wrote: >> On Mon, Nov 15, 2010 at 4:19 PM, ? wrote: Just make sure you keep in mind the difference between the specification and what is likely to be acceptable. ?One value is better suited to personal tinkering, the other to widespread propagation. >>> >>> Good point. As background to my questions Turtle Art 103 now supports sensor input. >>> http://wiki.sugarlabs.org/go/Activities/TurtleArt/Using_Turtle_Art_Sensors >>> As the specification stands, no teacher is going to conduct science experiments with external voltages. If the specification is changed to +-9v then they will have the confidence to conduct experiments with caution. >> >> Why not use 1.5V alkaline cells? ?Or measure voltage from a lemon >> battery? ?I can think of any number of safe experiments. > > Why not indeed. See > http://wiki.sugarlabs.org/go/Activities/TurtleArt/Using_Turtle_Art_Sensors#Lemon_battery Right. You can also do quite a lot of useful experiments using the built-in 2V bias. I'm not sure exactly what the problem is -- maybe Tony can offer a more precise objection? Perhaps he feels there needs to be more guidance given on how teachers can construct "fool proof" sensor experiments that are minimally dangerous to hardware, even if the teacher isn't watching every kid every minute? --scott ps. my rule of thumb would be "don't involve an external battery more powerful than a lemon" -- as I understand the protection circuits, there's no way you can connect the internal bias voltage coming from the microphone jack in a way that would damage the input. You can construct a lot of experiments (ie, most on the Turtle Art Sensors page) which are thus "guaranteed safe, even if kids make mistakes" on an XO-1.5/XO-1.75. But the "measuring AC amps" example should be moved to a separate "only with supervision and adequate care" page. (Maybe also the "Generating electricity" example also, although it would take a lot of turns of wire, a pretty strong magnet, and very vigorous motion to exceed 9V.) And the "Lemon battery" and "generating electricity" examples should additionally be warned against on the XO-1 --- maybe also the "burglar alarm", depending on whether the XO-1 is always safe if its inputs are shorted. ___ Devel mailing list Devel@lists.laptop.org http://lists.laptop.org/listinfo/devel
Re: Re: XO-1.75 microphone socket
On Tue, Nov 16, 2010 at 11:38 AM, Walter Bender wrote: > On Tue, Nov 16, 2010 at 11:19 AM, C. Scott Ananian wrote: >> On Mon, Nov 15, 2010 at 4:19 PM, wrote: Just make sure you keep in mind the difference between the specification and what is likely to be acceptable. One value is better suited to personal tinkering, the other to widespread propagation. >>> >>> Good point. As background to my questions Turtle Art 103 now supports >>> sensor input. >>> http://wiki.sugarlabs.org/go/Activities/TurtleArt/Using_Turtle_Art_Sensors >>> >>> As the specification stands, no teacher is going to conduct science >>> experiments with external voltages. If the specification is changed to +-9v >>> then they will have the confidence to conduct experiments with caution. >> >> Why not use 1.5V alkaline cells? Or measure voltage from a lemon >> battery? I can think of any number of safe experiments. > > Why not indeed. See > http://wiki.sugarlabs.org/go/Activities/TurtleArt/Using_Turtle_Art_Sensors#Lemon_battery Right. You can also do quite a lot of useful experiments using the built-in 2V bias. I'm not sure exactly what the problem is -- maybe Tony can offer a more precise objection? Perhaps he feels there needs to be more guidance given on how teachers can construct "fool proof" sensor experiments that are minimally dangerous to hardware, even if the teacher isn't watching every kid every minute? --scott ps. my rule of thumb would be "don't involve an external battery more powerful than a lemon" -- as I understand the protection circuits, there's no way you can connect the internal bias voltage coming from the microphone jack in a way that would damage the input. You can construct a lot of experiments (ie, most on the Turtle Art Sensors page) which are thus "guaranteed safe, even if kids make mistakes" on an XO-1.5/XO-1.75. But the "measuring AC amps" example should be moved to a separate "only with supervision and adequate care" page. (Maybe also the "Generating electricity" example also, although it would take a lot of turns of wire, a pretty strong magnet, and very vigorous motion to exceed 9V.) And the "Lemon battery" and "generating electricity" examples should additionally be warned against on the XO-1 --- maybe also the "burglar alarm", depending on whether the XO-1 is always safe if its inputs are shorted. -- ( http://cscott.net/ ) ___ Devel mailing list Devel@lists.laptop.org http://lists.laptop.org/listinfo/devel
Re: Re: XO-1.75 microphone socket
On Tue, Nov 16, 2010 at 11:19 AM, C. Scott Ananian wrote: > On Mon, Nov 15, 2010 at 4:19 PM, wrote: >>> Just make sure you keep in mind the difference between the specification >>> and what is likely to be acceptable. One value is better suited to >>> personal tinkering, the other to widespread propagation. >> >> Good point. As background to my questions Turtle Art 103 now supports sensor >> input. >> http://wiki.sugarlabs.org/go/Activities/TurtleArt/Using_Turtle_Art_Sensors >> >> As the specification stands, no teacher is going to conduct science >> experiments with external voltages. If the specification is changed to +-9v >> then they will have the confidence to conduct experiments with caution. > > Why not use 1.5V alkaline cells? Or measure voltage from a lemon > battery? I can think of any number of safe experiments. Why not indeed. See http://wiki.sugarlabs.org/go/Activities/TurtleArt/Using_Turtle_Art_Sensors#Lemon_battery -walter > --scott > > -- > ( http://cscott.net/ ) > ___ > Devel mailing list > Devel@lists.laptop.org > http://lists.laptop.org/listinfo/devel > -- Walter Bender Sugar Labs http://www.sugarlabs.org ___ Devel mailing list Devel@lists.laptop.org http://lists.laptop.org/listinfo/devel
Re: Re: XO-1.75 microphone socket
On Mon, Nov 15, 2010 at 4:19 PM, wrote: >> Just make sure you keep in mind the difference between the specification and >> what is likely to be acceptable. One value is better suited to personal >> tinkering, the other to widespread propagation. > > Good point. As background to my questions Turtle Art 103 now supports sensor > input. > http://wiki.sugarlabs.org/go/Activities/TurtleArt/Using_Turtle_Art_Sensors > > As the specification stands, no teacher is going to conduct science > experiments with external voltages. If the specification is changed to +-9v > then they will have the confidence to conduct experiments with caution. Why not use 1.5V alkaline cells? Or measure voltage from a lemon battery? I can think of any number of safe experiments. --scott -- ( http://cscott.net/ ) ___ Devel mailing list Devel@lists.laptop.org http://lists.laptop.org/listinfo/devel
