Help to choose some NXT sensors to buy

[happymark]

Hi All,

I am thinking to take advantage of current US shop.lego.com promotion. *$75 with free shipping

To help a FLL team , I am thinking to buy a light sensor.

besides that, what do you recommend? I only have a NXT retail set - means 3 motors with 1 ultrasonic 2 touch and 1 color sensor.

do you think I should buy a rechargeable battery with DC charger?

I do have some rechargeable AA batteries though.

Thanks!

Mark

[DLuders]

You should see what the First Lego League team wants to do with their robot. The Lego Light Sensor is a must, but there are many other cool devices for sale on this Shop.Lego.com webpage. The Lego 9693 NXT DC Rechargeable Battery could save the team a lot of money over time (compared to alkaline 1.5V batteries), but it is sold out until September 23rd. If you're not in a hurry, that would be a nice purchase.

During FLL competitions, recommend that you use new alkaline 1.5V batteries because they will provide MORE INITIAL AMPERAGE (and faster speeds) compared to rechargeable batteries.

[Phoxtane]

Ultrasonic sensors rank at the top of my list in usefulness. You could probably pick up another one of those. It never hurts to get more touch sensors as well; HiTechnic sells a multiplexer that allows you to attach up to four touch sensors to one NXT sensor port!

[Jetro]

Check current FLL regulations first. Last time I looked only the "standard" sensors were allowed, so they may not be able to use what you buy for them. The colour sensor may be an option if they don't have it -earlier kits came with the light sensor and the colour sensor is now allowed for use. Forget about multiplexors (LEGO doesn't sell those anyway).

A rechargeable battery could save the team quite some money, but first make sure they don't already have one as the Edu set includes one.

There's a good chance that what the FLL team would be best served with is additional parts to build their robot, o my advice is get them a Technic set with lots of handy parts.

[mescalinum]

do you think I should buy a rechargeable battery with DC charger?

I do have some rechargeable AA batteries though.

according to the printed pattern on the rechargeable nxt battery:

it is a 7.4V battery, which is rather unusual.

Using 6 rechargeable batteries you'd get 1.2V * 6 = 7.2V, so you get an extra 0.2V

however I do not understand this choice by LEGO engineers, since with alkaline batteries you get 9V, they could have put one or two more cells, resulting in 8.4V or 9.6V which is closer...

[Jetro]

The standard charge for a single Lithium-Ion battery pack is 3.6V. Put two packs in a rechargeable battery and you get 7.4. Adding a third would take the voltage above the recommended value for use with LEGO elements.

This voltage also applies to the rechargeable "train" battery many Technic builders have used in their MOCs.