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grum64

Lego Touch Sensor & Technic

14 posts in this topic

Good Evening

I feel guilty always asking for your help & not giving anything in return so please forgive me asking for your help yet again.

I've acquired a Lego Touch Sensor with a view to using it with my PF's but looking at it I'm now wondering if it'll work with them.

Any advice?

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You will probably need the old RCX type touch sensors - which worked with the 9V plugs. The newer mindstorm ones use the RJ45 connector... for the mindstorms brick. You might find some solutions to cross wire them, but will definitely need to equip the grandson with a soldering iron. ;-)

However if you already have the NXT / Mindstorms bricks, then you could use some of the patch cables which exist...

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NXTPrograms.com has this interesting webpage that outlines Touch Sensors being used with Lego Power Functions.

DCP_5136.JPG

Thank you. I'll take a look.

You will probably need the old RCX type touch sensors - which worked with the 9V plugs. The newer mindstorm ones use the RJ45 connector... for the mindstorms brick. You might find some solutions to cross wire them, but will definitely need to equip the grandson with a soldering iron. ;-)

However if you already have the NXT / Mindstorms bricks, then you could use some of the patch cables which exist...

Thank you for the info.

Grandson + soldering iron + irate daughter in law = very unhappy Grum!!

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Grandson + soldering iron + irate daughter in law = very unhappy Grum!!

Well they have to learn sometime ;-)

Anyway here is the image link I had in mind last night

879.gif

This is directly 9V compatible and appeared in 16 sets. Using the 9V to PF adapter, im assuming it would just provide on / off command onto the 9V power line. Two thirds of the way down Philo's page is a link to the schematics of PF.

diagram.gif

Clearly the old 9V touch sensor - which apparently has a switch to short 9V to ground would cause any enabled PF system to start and stop. But someone would need to check if it really works

Fig5.gif

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My touch sensors which came with 8479 Barcode truck no longer work :cry_sad: (the motor and barcode scanner still work though).

This made me believe that unlike Lego components, longevity of Lego electronics bits is much lower.

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Touch sensors (either old RCX one or NXT one) are sensors and are NOT suitable to power devices. Their internal resistance is too high for that use (about 500 Ohms for RCX sensor, 2.2k Ohms for NXT sensor). I guess they might work with the really low power PFS LED lamps, but then you have another problem, the "normal" connexion you can get from a PFS <-> 9V cable puts the switch in parallel with supply and device, while a switch requires a series connexion!

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Well they have to learn sometime ;-)

Anyway here is the image link I had in mind last night

879.gif

This is directly 9V compatible and appeared in 16 sets. Using the 9V to PF adapter, im assuming it would just provide on / off command onto the 9V power line. Two thirds of the way down Philo's page is a link to the schematics of PF.

diagram.gif

Clearly the old 9V touch sensor - which apparently has a switch to short 9V to ground would cause any enabled PF system to start and stop. But someone would need to check if it really works

Fig5.gif

Very informative. Thank you very much.

The TS I have is the same a the one in your posting. Old or new, I don't know but it'd be handy if it could be used.

Thanks again.

Grum

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Slightly off topic, but related with electric current,why does the technic control center 2 not lego power function receivers? :angry:

Edited by Alasdair Ryan

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Unfortunately I do not think the touch sensor is directly compatible with the PF system, you will need a device intended to work with them like the RCX brick or barcode truck scanner (code pilot).

Slightly off topic, but related with electric current,why does the technic control center 2 not lego power function receivers? :angry:

The remote reciever is powered by the outer two wires (9v and 0v shown in the above diagram) and the extention wire being powered by the control centre is only powered on the two inner wires (c1 and c2 in the above diagram). So you may need to bridge the contacts, as shown in this TBs post.

http://technicbricks.blogspot.co.uk/2009/11/tbs-techtips-28-connecting-pf-receiver.html

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Touch sensors (either old RCX one or NXT one) are sensors and are NOT suitable to power devices. Their internal resistance is too high for that use (about 500 Ohms for RCX sensor, 2.2k Ohms for NXT sensor). I guess they might work with the really low power PFS LED lamps, but then you have another problem, the "normal" connexion you can get from a PFS <-> 9V cable puts the switch in parallel with supply and device, while a switch requires a series connexion!

Philo is right - and I did not take enough time to explain. These sensors cannot be used inline with a motor to switch it on / off. Since most of the power supplies are voltage regulated, this would allow 9V / 500ohms = 18mA through the resistor which would influence how a light is perceived, and might slow a motor but is not the same as a start / stop. Normally sensors would be wired to some form of transistor which in turn switches high power components.

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Unfortunately I do not think the touch sensor is directly compatible with the PF system, you will need a device intended to work with them like the RCX brick or barcode truck scanner (code pilot).

The remote reciever is powered by the outer two wires (9v and 0v shown in the above diagram) and the extention wire being powered by the control centre is only powered on the two inner wires (c1 and c2 in the above diagram). So you may need to bridge the contacts, as shown in this TBs post.

http://technicbricks.blogspot.co.uk/2009/11/tbs-techtips-28-connecting-pf-receiver.html

Thank you for taking the time to help.

Philo is right - and I did not take enough time to explain. These sensors cannot be used inline with a motor to switch it on / off. Since most of the power supplies are voltage regulated, this would allow 9V / 500ohms = 18mA through the resistor which would influence how a light is perceived, and might slow a motor but is not the same as a start / stop. Normally sensors would be wired to some form of transistor which in turn switches high power components.

As with my other cries for help, thank you one and all. You really are the best.

Isn't the Eurobricks 'family' great to be part of!

PS Anyone need an Unused Lego RCX Touch Sensor?

Edited by grum64

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Isn't the Eurobricks 'family' great to be part of!

Yes, it really is :classic:

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I was going to have a NXT for my birthday. Until i had a nice long chat with someone at Lego NXT department about it and found out that there not really compatible with Power Functions. And Lego no longer do the patch leads. Seems a shame that 2 systems and no interface between them.

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