Solar Charger Project

I have the basics out for this project. The robot part will be incorporated later.

Right now this is the setup:

solar panel -> battery box -> output

soon it will be:

solar panel -> battery box -> output panel ->output


Battery box-> NXT  <-> output panel











Two series circuits that are interconnected.

There is more than a SPDT switch in the battery box, but this is for simplicity.

The NXT would be connected to the blue and green wires through an RCX end and 2 cables to Port A and Port 2 The program is done, but it needs to be edited.

Printer + Robot update.

Both robots are now operating seamlessly. I renamed them – Jared [that’s my personal robot, will not be seen very often in JP, unless a dual NXT robot is used] – and – Jared JP [that’s the general purpose robot]

I fixed the screen, and best of all, found that it coldn’t hurt to update the firmware, on the both of them, to 1.31 [one was under 1.29, the other was really unupdated and at 1.05!]

I also fixed a problem where one of the batteries would not function at all. Apparently the one on Jared JP [originally Jared A., the second one I’ve bought intentionally] had totally depleted in about 5 minutes [that’s the normal properties of a Li-on, they last at high voltage really long and then plummet. That’s what this did and took forever to charge, and made a mental note – as soon as its 7 volts – charge it. As soon as it hit 6.9, it just dropped like a rock to 5, where the NXT automatically shut off. It takes a while to get from 5 back to 7.2v.

Printer LDD + photos for your reconstruction if you want to try it. Some of the printer parts are impossible to build in LDD without great difficulty, so I left them out and took pictures of the actual thing.


Latest problem:

The robot that has been left over for the printer has been sitting a while and when I turned o the NXT, the screen was not working correctly. Via Bricx, I could connect and see that the NXT microchip was indeed sending the normal screen, but the image was halfway down the screen. But after going to get some dinner, and leaving it on, it somehow fixed itself in 10 minutes, and haven’t had any problems [except that I can’t find my battery charger for the NXT power pack]. I think one of my ultrasonic’s are broken beyond repair, so I might have a take-apart of that to see what could be the problem, maybe a loose connection or something… I’ll have to test it again, maybe it just wan’t sending anything…

The solar charger works great now that the sun is out. I actually got above a charge of 1.2 volts in the rechargeable, so that’s really nice [my charger usually leaves them at 1.15v]. The sun looks bright again today, maybe I’ll get a full 1.5v! The NXT agrees with me and putting all six into the robot measures out 7.4v, = 1.23v. Nice.

Now just to find the charger. Sorry that I lost the enthusiasm to build the printer any farther, but I will publish building instructions… Hopefully it has the rack gears in the library of parts…

Square Wheels Robot

I got tired of waiting for the sun to come out to take a video, so I got a little off-track and made a cool project: A robot with square wheels. It looks really weird, but sounds cool as can be, almost like a 5hp engine on idle.


Preview for Solar Battery Backup Device using Lego Power Functions

There will be photos and video of the project coming soon, but I can tell what I have so far.

I’m taking a shoe-box and converting it into a battery backup. Although I’m only using a power functions battery box filled with 6 rechargeable 2400mAh batteries, creating a total of 7.2v and 14400mAh, it’s only powering LED’s, which use about [according to my research] 10-20mAh. That would amount to [with 20mAh] about 720 hours of light in one charge, with one LED. If I ran LED’s for 8 hours [overnight], then I could run at least 30 LED’s. That would be plenty of light for a room or two… and during the day I could charge them with the solar panel, and use a small power regulator, maybe the NXT, but could be as simple as running a motor while charging in the sun to keep the rechargeable batteries from overcharging. I could run the NXT all night easily on a rechargeable battery pack that I bought for it from Lego Education [a site full of bulk Lego’s!], but I could only trust the power pack and a wall socket with the best power-strip with all sorts of protection for that.

The great thing about Power Functions is the plug. It has 4 wires, as follows:

positive [0v]

variable [the direction of the swich on the battery box or the separate switch uses this to run the motors and lights]

variable [reverse charge of the one directly above for return voltage]

negative [full battery charge, for me, its 7.2v]

Using the two outer ones, I can charge the battery without impairing the ability to run the motor in either direction. This is really useful, although I don’t like the design for the external switch because it doesn’t work independently of the battery pack to send a voltage to the motor or led’s – only the battery pack can use the outer wires, and the motor and switch can only use the inner ones [but the switch, regardless of position, will always send voltage through it on the outer wires. I assume this was used for the Infrared receiver and other parts to work with it, independent of the position of the switches. The good thing is that when you switch the battery pack to the off position, it shuts off all the wires, including the outer wires. This in some places may not be extremely useful, but the use is good here because I can control it better from the external switch anyways… If you really didn’t like it, I’m sure it’s not too hard to take apart the battery box and edit that problem, but I like it in it’s “vanilla” [original] form.

I hope to have pictures out soon, maybe a video too.

power functions port wiring by jared

Power Supply Project

Slightly off the topic of Robotics, I have built a power supply to take USB or a 14v power pack and make a usable end out of it for running motors, fans, and other useful equipment that needs to be tested before installed into something.

As seen on the Google page:

I wanted to make a power supply to be able to plug into multiple sources for DC voltage. Two voltages are made from the device, 5v 200mA from the USB, and 14v 200mA from the power pack. I do not have a power regulator making the 14v into 5v, but that would be a nice touch in the future.

Dance Robot Project

This robot has sucessfully done its task and I am done supporting it now, on to other projects. There is no Google page for this project yet, but I have gotten to uploading some YouTube videos. The main objective was to make a robot that could tell both how loud something is, and then use that information to find the bigger of beats.

YouTube videos: