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Hi there, Being a *complete* dufus when it comes to things like electronics, I've no idea how to start creating my own sensors, but I feel I have to start somewhere. I've thought about creating a LEGO Electromagnet (uses the motor connectors to be (...) (23 years ago, 14-Apr-01, to lugnet.robotics)
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| | Re: LEGO Electro-magnet
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I have been thinking about this very thing recently. It's actually pretty simply. For the simplest version, all you need is a nail or screw (preferably with a lot of soft iron in it, otherwise it will tend to stay magnetized to some extent once the (...) (23 years ago, 15-Apr-01, to lugnet.robotics)
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| | RE: LEGO Electro-magnet
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Thanks it worked! I had some magnetic wire from a Stiquito set I just built, to I managed to get a simple one working, but I couldn't connect it to the RCX for some reason. I'd attach it to one of the LEGO wires (do the order of the connectors (...) (23 years ago, 15-Apr-01, to lugnet.robotics)
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| | Re: LEGO Electro-magnet
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James Matthews <lego-robotics@crynwr.com> wrote in message news:MABBKIIIBOMODJG...net.com... (...) built, (...) of (...) the (...) I had the same battery warning when connecting some large non-Lego motors to my RCX, and I'm fairly sure the reason (...) (23 years ago, 15-Apr-01, to lugnet.robotics)
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| | Re: LEGO Electro-magnet
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Hi all, there is another thing you should think about. When using an electo-magnet, you use a coil. This coil stores energie, so if you switch it off, the coil gives this energy free. (This is the energy your ignition-sparks gets from an ignition (...) (23 years ago, 15-Apr-01, to lugnet.robotics)
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| | Re: LEGO Electro-magnet
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Rainer Balzerowski <balze2@gmx.net> wrote in message news:GBuG0y.EAv@lugnet.com... (...) electo-magnet, you (...) gives (...) diode (...) (Or use (...) hammer (...) Because motors also contain electromagnets, I imagine they would have the same (...) (23 years ago, 15-Apr-01, to lugnet.robotics)
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| | Re: LEGO Electro-magnet
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Hi Philip, may be, but I would chose the safe side (We did with our 6.270 board and used 2 diodes, who cares about 2 diodes). BTW I'm not sure what happens with the energy in an electro motor. I can imagine that this energy (resulting in a magnetic (...) (23 years ago, 15-Apr-01, to lugnet.robotics)
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| | Re: LEGO Electro-magnet
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Rainer Balzerowski <balze2@gmx.net> wrote in message news:GBuGyD.Fzn@lugnet.com... (...) used 2 (...) the (...) electro (...) I've found a book which mentions this, and talks about using 'flyback diodes' when "switching inductive loads such as (...) (23 years ago, 15-Apr-01, to lugnet.robotics)
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| | Re: LEGO Electro-magnet
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Well, good work Philip. Good to be sure about this. I was only afraid that you'll frie your RCX, because of not knowing this effect. Regards, Rainer P.S.: Learned something, not unload diode, but flyback diode ! ;-) (...) (23 years ago, 15-Apr-01, to lugnet.robotics)
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| | Re: LEGO Electro-magnet
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The easiest way to get an electormagnet is to hack a small 12 volt electric clutch or brake. These have a powerful electromagnet that still has good strength when run at 9 volts. Most of them will not overload the RCX. Edmund Scientific sells one, (...) (23 years ago, 16-Apr-01, to lugnet.robotics)
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| | Re: LEGO Electro-magnet
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Another idea for a controllable magnet (one that could be turned on or off): Machinists use magnetic bases to hold measuring instruments firmly onto the steel ways of lathes and milling machines. The bases have a knob that permits the machinist to (...) (23 years ago, 18-Apr-01, to lugnet.robotics)
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| | Re: LEGO Electro-magnet
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There is a description of a magnet actuator at Andreas Peter's site: (URL) (see Elect.Actuator) But two modifications IMHO are needed to this design : - Use heavier duty diodes than 1N4148 indicated in Andreas shematics. 1N4148 is rated 20mA and is (...) (23 years ago, 19-Apr-01, to lugnet.robotics)
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| | Re: LEGO Electro-magnet
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(...) Hi Philippe, you're right, but you don't need this flyback diode, as Philip Taylor mentioned here : (URL) you don't need a flyback diode, you also don't a diode in series. Rainer P.S.: I had the same ideas than you mentioned above ;-) (23 years ago, 19-Apr-01, to lugnet.robotics)
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| | Re: LEGO Electro-magnet
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Hello Rainer, True! But simplicity sometimes takes a long time to be acheived ;) But there may be some use in flyback and series diodes: Andreas says that his magnet consumes 9mA, below what is available through sensor ports in active mode. So a (...) (23 years ago, 20-Apr-01, to lugnet.robotics)
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| | Re: LEGO Electro-magnet
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Hi Philippe, (...) Hmm, I guess they are NOT protected. (...) Not sure, (I'm not an electrical-engineer please Andreas Peter, help :) ) But, when the coil has a consumption of 9mA at 9V it's 1k. (81mW) So if I undestand it right, you're in parallel (...) (23 years ago, 20-Apr-01, to lugnet.robotics)
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| | Re: LEGO Electro-magnet
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To be more precise: in passive mode there is a 10K pullup (to 5V) introducing some current (0.45 mA) in the coil. This small current may be enough to retain something stuck to the magnet... Philo (...) (23 years ago, 20-Apr-01, to lugnet.robotics)
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| | Re: LEGO Electro-magnet
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(...) I think this could happen. Even without this low current present all the time, an electro magnet powered by a DC supply always in the same direction can develop a residual magnetic field (samll things would stay stuck even after the electro (...) (23 years ago, 21-Apr-01, to lugnet.robotics)
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