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Sundsted
05-09-2010, 11:52 AM
Hello, nice to see all these robot people. I work for a midsized Sheriff's Office in Oregon and supervise our Remotely Operated Vehicle Team. Our main robot is a big bomb squad type robot. We have been looking for a small surveillance robot for some time. Most of the ones on the market run about $20k. My commander decided that we should see if I could build something for under $2000.

I did a bunch of research and found that Traxxas makes an RC car that has a 2.4GHz controller. I got the two wheel drive version to save some money. With a 2.4GHz controller I can use high gain WiFi antennas to increase the range. I used two RC 7.2 volt wired in parallel to help increase run time.

For the video system I used to IP cameras, a Panasonic BB-HCM531A (http://www.newegg.com/Product/Product.aspx?Item=N82E16881180021) and a Panasonic BL-C1A. The BB-HCM531A is a P/T for the front drive and surveillance camera and the BL0-C1A is a fixed rear mounted reverse camera. This is connected to a Linksys WRT54GL router flashed with DD-WRT which in turn have two high gain antennas. All this is powered by a NiMH 12volt 2300aMH battery. I currently have an issue as I am only getting about 20 minutes of run time from it. Thinking I may need to upgrade to an 18volt LiPO battery.

I then built a body to place this all in. I used aluminum to keep the weight down as much as I could. All the body components were then siliconed to keep them water resistant.

Right now I have about $1300 into the build. It works pretty well, other then the run time on the cameras. I am considering adding a serial port to the router and then converting the drive systems to WiFi as well. There are a couple websites showing how to do this.

I will attach some photos if the forums will let me.

Tristan

RavenW
05-09-2010, 07:45 PM
Sounds like you did a good job. When you get your new battery just get the highest mAH rating that you are willing to pay for. With 4600 mAH you should be able to get around 40 minutes of run time. What kind of range are you getting with this set up?

zoomkat
05-10-2010, 12:52 AM
Probably a thing to do is measure the curent being drawn by the various components to see what are the big power users and see how they can be better managed. $560 is a chunk of change for a network cam.

Sundsted
05-10-2010, 10:07 AM
Yes, I am looking at a 4500mAH battery for it. As far as range, with high gain antennas I am getting about 150, maybe 200 feet non-line of site. I really want to get to about 400 feet non-line of site. I bought a 500mW WiFi booster to put on the controller transmitter as it is only 10mW. I have yet to test this much but so far the range seems much better.

The front camera was a bit spendy but I wanted a pan and tilt. It was cheaper then some of the other options and that model is water resistant. I am having some pauses in the video feed from that camera which does not make driving it real fun as a 1 second pause at top speed can be dangerous! I am thinking about adding another fixed mounted drive camera, the same as the rear camera. The rear facing camera works very well and streams without and pauses.

If anyone else has any ideas please share them. I am pretty new to this but am enjoying the heck out of it.

jes1510
05-10-2010, 11:53 AM
Yep I wanna see pics. This sounds like a great little project. Nice work!

RavenW
05-15-2010, 03:13 PM
This thing is for official police use right? One thing to keep in mind is that microwave ovens make excellent Wifi jamming devices so if anyone nearby decides to have a hot pocket you may lose your feed. An idea would be to get something like a cellular router or an adapter (like a USB wifi stick but for cell) for at least the drive camera as a backup. Cell signals and architecture are far more prescient and robust than wifi in urban areas which could give near unlimited range within a city. Unfortunately I know of little more than the fact that these things exist so you may want to just read up on them before you do anything. Sorry, I have a mild obssession with redundancy.
Like zoomkat said, look for the highest power users and try to manage them better for longer battery life.

Sundsted
05-19-2010, 01:39 PM
Yes, but only as a back-up or secondary unit. Our main robot is tethered and can't be jammed.

jdolecki
05-19-2010, 04:48 PM
Can you post so pictures of you other robot you use?

thanks

Sundsted
05-20-2010, 09:31 AM
Sure, we use a Remotec Mini Andros. It is about 6 years old, so it's an older robot but it works well for what we use it for. The other nice thing is the warranty has expired so I can tweak it as much as I want without voiding the warranty! :)

kwal
05-25-2010, 02:58 PM
Wow this seems well thought out. With the battery if it was me I would use a 4 cell lipo not a 5 cell for a few reasons, 1 they are cheaper so you can get a higher mah rating, 2 a little easier to find for replacement and 3 they're lighter, you already put more weight on the slash than Traxxas had intended on and will put less strain on the motor/esc.

One thing have you changed the gearing on the vehicle, because you added more weight to it it will put more stress on the motor. The motor that comes with the Slash isn't a horrible motor but when they are stressed more than just bashing they have a so-so performance. Also by lowering the gearing you'll get better low speed control and longer run time.

Sundsted
05-26-2010, 12:33 PM
Yes, I changed the gearing but it still did not help much as they are designed to go fast. I just bought a Traxxas Summit rock crawler and am planning on using that instead of the slash. It is way slower and designed to climb things. It also runs two batteries at 16.8 volts which I can use to power my equipment inside. If it works then I will upgrade to LiPo from there.