Lawmate wireless transmitter help....

[Kitsu]

Hey,

Ok, so I got my FCC license (wooo KC2JZB!!!), and I got my 100mw Lawmate unit from Y2B, but I'm having some issues...

The camera I plan on using as of now is a cmos camera.

There are 4 wires on the board, and as shipped, 3 connectors came off of the camera.
---A power plug (with red and black), and
---RCA yellow (for video, has yellow and black) and
---RCA White (white and black). As far as I could figure out the camera doesnt have a mic, and in playing with the camera hooked upto my TV before getting the TX I never used the white plug.


Each plug has a ground that meets at a little glob in the middle, and then goes to the board as one ground... So all told, 4 wires on the board.

The camera is rated at 8v but I've used it off of a 9v battery... the TX is 12v... I planned on powering both off the same 9v battery.

I connected the yellow video wires together. The red power leads I connected to the positive on the battery
. Not knowing what really to do, I connected all of the grounds together and connected that to the battery negative.

Of course, it doesnt seem to work....

Could it be that the TX will not operate at 8v or 9 or whatever it is? is my problem with the grounds? On all of the stuff I saw on Y2B's site his camera always had a "video ground". I don't think my camera has that.

If I'm not making sense I can take some pics or make a diagram.

Thanks,
Andrew

[Mr.RC-CAM]

Could it be that the TX will not operate at 8v or 9 or whatever it is? Lawmate operation at 9V or less is not reliable. In addition, some "9V" style rechargable batteries are actually only 7.2V. Try 10VDC-12VDC and see what happens.

Also, are the Tx and Rx chnl select switches set to the same operating freq?

Congrats on your ham ticket!

Regards,
Mr. RC-CAM
www.rc-cam.com

[yb2normal]

Lawmate operation at 9V or less is not reliable.

Agreed. In my experiments the transmitter would reliably start-up (begin transmitting) down to 9v. Below 9v it would start up intermittently.

Andrew, contratulations on getting your ticket! Please tell everyone else who has been procrastinating how painless the process was :)

Bill
Black Widow A/V (http://www.BlackWidowAV.com)

[Mr.RC-CAM]

Bill, Congrats to you too! I see that you are now legal too. Welcome to the club.

Both you and Kitsu got your license issued on the same day. Should have gone for the "friends fly free" discount. ;)

Regards,
Mr. RC-CAM

[William A]

Originally posted by yb2normal
Please tell everyone else who has been procrastinating how painless the process wasYes, please do, for I would be one of those procrastinators procrastinating.

Some of those sample questions got me somewhat stumped. I've been studying, but just doesn't sink in like it use to.:rolleyes:

[Kitsu]

Yes, taking the test wasnt really too bad.... I bought the book a while back... studied off and on, and the week before the test took practice exams online like 4 or 5 times a night (Would just whip through them). Worked fine. Heck, they made me take the general class test, and having not studied a lick for it I only missed like 13? (9 max)... So its not too difficult.

Ok, so back to the transmitter..... I'll try hooking it up to something with higher voltage.

However, regarding the grounds on the TX and my lack of grounds on the camera, should I just connect them all together? And if I am powering the tx and the camera seperately, what do I do?

A little diagram of how it is right now....
~A

[Kitsu]

And a revised diagram (of course I'll get something like the spider board, but for now this will do for testing).

BTW, thanks Bill for the quick shipping.

[yb2normal]

Andrew, you can tie all the ground together.

William, in terms of the process, I just took the online tests at QRZ.COM and EHAM.COM over and over again and supplimented it with the book. The electronics theory section was easy for me since I'm an electronics enthusiast. The book does a good job of describing why a particular answer is correct, so I learned a lot about atmospheric concepts, as well as RF safety. The stuff I ended up just memorizing was the frequency ranges of the various bands. Fortunately there weren't a lot of those questions on my test.

From there it was simply a matter of going to ARRL.COM and finding a test site near me... they make it really easy and show you the closest sites to you (mine was at a local church) as well as the scheduled test dates. I called up the contact lady and said I wanted to take the test, and she said "see you there". That's when I really started studying... as soon as I had signed up for the test date :)

Bill
Black Widow A/V (http://www.BlackWidowAV.com)

[Kitsu]

Ok, so I'm gonna put my 3 "?" grounds together and we'll see how it goes....

time to order that little voltage converter thing.

My test I didn't even have to sign up for, called the number but it was some dude's voice mail and it was "if you are calling for the test blah blah, if you need to speak with me in person leave a message"... So I just showed up at the site. Was there only about an hour. Easy as cake.

Anyone want to buy my technician class study guide? hehe
~A

[Kitsu]

WOOOOOOOOO

from one end of my table to the other the video quality looks great!!!

Now off to order the parts to make a spider board :)

Thanks guys.

~Andrew

[Kitsu]

Ok, I ordered the DC -- DC converter that Bill uses on his spider board, and have set mine up as closely to his as I could get. Plugging in a slightly discharged 9v battery, I get 12.2v on the Vout and the cell voltage on the input lead.

Connect the system, power up the receiver, and it doesnt work. So how come it worked when I powered the stuff off of seperate power sources, but when I get the DC DC converter and it is outputing the proper voltages, I get static???

I double checked the channel, and have installed the electrolytic cap as per the spec sheet.

Now what?

~Andrew

[Mr.RC-CAM]

Describe the "9V" battery in detail.

[Kitsu]

I am testing with 2 "9V" batteries...

one is an energizer nimh, 9v sized batt, gives 7.2 when charged (about 7 right now) and the other is a duracell 9v, giving 7.4 now....

The power lead to the DC DC converter is a 9v style battery connector.

Is that the info you wanted?
~A

[yb2normal]

Andrew, do you get video AND audio static? Or can you hear the audio on the rx...

I'm assuming the RX is being powered by 12v.

Did you measure the input voltage while the setup was under load? It might be dropping farther than 7.2 volts, in which case your 9v camera will start giving you problems.

Finally, recheck the output voltage of the converter... the TI dc-dc converter is not reverse polarity protected, so even one quick brain-cramp with a reversed voltage on the inputs will destroy it.

Bill

[Mr.RC-CAM]

Is that the info you wanted? Almost. What is the 9V pack's mAH rating?

I am going to assume that you are using those little rectangular 9V packs that are shaped like a "transistor radio" (rectangular) battery. If so, these have VERY limited current delivery abilities.

You need to use a pack that is 600mAH or higher. These larger packs can deliver the necessary mA's to reliably startup the DC-DC's oscillator while under full load.

BTW, the use of a nifty PT5041 DC-DC IC supply was first pioneered in the RC-CAM3 project a few years ago. It has worked so well that it now has a huge following in this R/C video application. To see where it all began, please visit the RC-CAM3 project page.

Best Regards,
Mr. RC-CAM
www.rc-cam.com

[Kitsu]

Yea, the 9v is a stupid little brick thing..... so maybe you are right. Tho my camera only needs 80mah, the tx is what? 150 something mah? but you are saying that the DC DC needs alot more to start working?

Earlier tonight before I came here I was getting 12.2 on the lead out, and the V for the camera, I just went back and checked, only got like 3 something on the battery, and like 5 on the Vout... so maybe both of thoes batts are dead now??

As for earlier, I was getting both static.

And as far as I know I have never hooked up the converter backwards.

if you guys can think of anything overnight or tomorrow I'll try it.... tired of messing with this now :)

Andrew

[Mr.RC-CAM]

Tho my camera only needs 80mah, the tx is what? 150 something mah? but you are saying that the DC DC needs alot more to start working? The DC-DC does not covert power, it converts volts. Since the Tx needs 12V at 150mA, that is 1.8 Watts. In a perfect world, to support 1.8 watts, the DC-DC will required 250mA at 7.2 volts. Factor in conversion efficiency and the current draw will exceed 300mA. Account for startup currents and you might hit 1000mA peak.

You need a better battery.

Grab a common 600mAH 4.8V Rx NiCD packs and try again. Once you prove it works, then try smaller packs. Frankly, anything under 600mAH is going to give you grief.

Regards,
Mr. RC-CAM
www.rc-cam.com

[yb2normal]

Do use all the capacitors recommended on the datasheet for the dc-dc converter, even the optional ones. Better safe than sorry.

[Kitsu]

Ok, after 2 days of doing various stuff not getting online, I have a working transmitter.

Thanks Mr. Rc-Cam for the reminder that duh, its not as simple as adding current draw,

Using 7 cells (250 mah AAA) I was able to get the unit to work. AND, I was even able to power my Mini Max and the transmitter off of the same pack. I got my first flights from it earlier tonight.

Bill, I have the required cap but will go back and install the optional ones. If there are any precautions you have (espeically regarding running both the TX and the plane off of the same batt, please let me know.

I am in the middle of formatting my other comp, but after that I'll hook up my new firewire card and get some clips online...

Thanks for the help!
Andrew

[yb2normal]

When sharing the main rc battery pack it is especially important to do a range check... the switching converter produces some noise that might or might not affect your installation.

Also note that if you run the battery to the BEC cut-off, your video system will still be drawing power and could potentially draw the battery down to the point that your RC system becomes non-operational. When I go up for video flights and I'm sharing the battery, I always bring it down with power to spare.

Haven't had a crash yet, knock on wood :)

Good luck, I can't wait to see the video!

Bill
Black Widow A/V (http://www.BlackWidowAV.com)

[Cash Traylor]

Does anyone have a manual for these transmitters (Lawmate, Futurehobbies, BWAV)? I have the 1 watt version, but they are all similar. I am trying to figure out the dip switches. Three dip switches and 8 channels. I know it can be done, but what are the sequences other than guessing. Anyway, I'd just love some more data other than the specs that I have found online.


Thanks in advance,

Cash Traylor