Prop Based Multi-tool

CassLan

Hi all,
I've had an idea in my head for a while and I want to make it a reality, I was hoping for some feedback on this idea. I install CCTV equipment, when my guys or I have to troubleshoot an outdoor camera, it usually goes like this:

Get up on the ladder
Unscrew the housing
Test Camera power with a Multimeter
Attach portable battery powered screen to camera's video out to see if camera produces an image
Test Video cable to DVR by attaching a portable DVD player to the Video Cable and seeing if we get a SONY logo on the dvr [noparse];)[/noparse]

So getting on a ladder with all that Smile is annoying,·and doesn't include·wire cutters/strippers/connectors...etc

I'd like to use one of Brilldeas 3.0" LCDs (really psyched since my typical portable screens need 12v)
I'd like to use a prop for the rest:

So Several Modes of operation:
I want this device to read the presence of low voltage (0~28V DC & AC) and display on screen
I want to be able to test for continuity with a display on screen and possibly a buzzer
I want to be able to connect a Video source to it to display on the screen (test the camera)
I want to be able to have a Video signal generated by the Prop (test the video cable to DVR)

I'd like this device to be small, run off standard batteries that can be bought at any store, and be rugged as hell...like if it gets dropped off the ladder [noparse];)[/noparse]

I started this a while back and got stuck right away at the voltmeter function, I bought some multi-meter MAXIS chips that where $28 each! They required soooo many external components etc..and It just got too daunting.

Being that a typical portable screen for "CCTV" use is $100+ I figure I can make something that would kill multiple birds with one prop [noparse];)[/noparse] This would be a valuable tool for me and my crew to have.

Any Ideas on how I can read those kind of low voltages being DC or AC?

Thanks,

Rick


·

simonl

@Rick: Oooh, that's a nice application I wish I could help with the voltmeter - I'm sure someone'll be able to chime in though.

Why not just make a start with the other bits? You know the Prop can do them all - and you'll be able to realise a useful tool anyway

Keep us updated.

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Cheers,
Simon

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www.norfolkhelicopterclub.com

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localroger

@CassLan, if you are just interested in "is it working" as opposed to "accurate enough for the ISO 9000 auditors," the Prop can do its own ADC with just a couple of resistors and capcitors -- I'm working on some functions using that now. The best thing is that since it's software you can jigger the bit count to trade accuracy for bit rate or vice-versa. Check this out:

http://forums.parallax.com/forums/default.aspx?f=25&m=115264

There's also a "mic to scope" demo in the OBEX based on this.

I think you might have a problem using BrillDeas' LCD's to display someone else's video. The Prop can't do frame capture because it doesn't have the RAM. You might have better luck bolting an add-on to a medium end portable DVD player, one that has NTSC A/V inputs. Most of the 8 inch up units do. The 7 inch units don't seem to. I am currently working on hacking the Philips PET702 to be a prop portable display, and I can guarantee that it won't display standard video without a lot of expensive conversion.

CassLan

@localroger,

Thanks! I will check that out now!

For the video testing function, I was going to have a switch that would direct video input to the screen from the internal prop, OR the externaly mounted BNC connector. If the LCD can display video generated from the prop than it can display CCTV video. I figure when the switch is in the position where the screen is displaying the prop video, that external BNC connector will also serve as a video out (for the Video cable testing)
So just to clarify, when using as a video test screen the prop probably won't even be powered on.

I will check out that voltage display and post updates!

Rick

CassLan

OK so based on that post Roger (http://forums.parallax.com/forums/default.aspx?f=25&m=115264)

If I place a voltage divider..like /10 and assume I never will be in contact with more than 30 volts, than I should be good.
I just need numerical values, I dont need a waveform on screen. How will I be able to tell if its AC or DC?
Luckily if its AC I know it will be 60hz..no 1khz [noparse];)[/noparse]

Rick

Post Edited (CassLan) : 5/8/2009 12:52:49 AM GMT

CassLan

Does anyone think this will fly? or will it just fry the prop?

Rick

Hmmm.. if the voltage happens to be DC then it will never get past the first cap right?




Post Edited (CassLan) : 5/8/2009 1:19:37 AM GMT

Tubular

Rick,

Some time ago I was playing with a relatively cheap ($30ish) multimeter that had RS232 output. Jaycar QM1535 or was it 1538. The output stream was literally the lcd segment bits sent once a second across the RS232 link. The plan was to fit a 433Mhz transmitter for wireless logging for under $40 for monitoring power usage. Then they stopped selling in :-(

Anyway the point is the Multimeter made a really good front end that takes care of a lot of stuff for you. It puts it into RS232 which you could read easily with the prop. It has a 'debug screen' showing the live voltage reading. Its also a good form factor for being able to fit the 3" screen and prop on the back face, has battery holders, and uses standard probes which you're used to. When you get time you could develop more 'scope' functionality with an ADC for higher freq signals... if the propscope doesn't come out first

just my 2c

tubular

CassLan

That sounds like a usefull device. I will look into that, thanks!

Tubular

This is what I'm talking about, a newer model for US$42 but it does lots and has optical isolation on the RS232
users.tpg.com.au/users/p8king/qm1538.htm

(edit) They also provide demo code in Visual Basic to decode the LCD data stream

localroger

@CassLan -- yeah, you have to omit the first cap to do DC. The circuit does work without it. (I'm doing DC myself, I'm measuring the output of an instrumentation amp reading a wheatstone bridge strain gage.)

For AC vs. DC, you will probably be able to observe the actual AC waveform at typical sample rates for that circuit. If you're using Spin and not sampling very fast you should probably use a cap between the front of the 1K and ground (probably following another resistor) to smooth out fluctuations. The Prop is capable of very fast ADC and if you just take random samples of high freq data at low freq, you can end up sampling noise spikes and getting very weird results.

Note you do need to use something like a protoboard and keep lead lengths short on the 1K resistor between pin8/pin9 and the .1 uF caps, because the frequencies are pretty high there and there are coupling and L/C issues. Breadboards like the Demoboard don't work for this. I have mine on a Protoboard with normal thru-hole components in the normal holes around the Prop chip and it's doing 16 bit conversions at about 1200 Hz. There's more noise than I'd like but I think my instrumentation amp isn't happy with the power supply. I think the ADC is working but there is drift on the input signal before the Prop even sees it according to my DVM.

Another way to handle the AC/DC thing is, instead of having one test lead to ground, have one test lead to ground via a 11K resistor and replace your 18K with a 7K. (Your device will be battery powered, right? It won't care about true ground.) Then you will see the full AC waveform, but zero will be offset so that you can tell it's going negative with the positive-only Prop ADC. (Or jigger the values, you probably get the idea.) Or you could use a smoothing cap and go old school and just have a separate AC input with a diode inline.

I don't think BrillDeas' LCD display will accept NTSC video; I think they had a thread about hacking a driver for it. Remember, while the Prop can genearate standard video, it can also generate NONstandard video, so just because the Prop can drive a display doesn't mean you can hook that display up to your standard DVD player. LCD's are notoriously nonstandard about this, so be sure before buying that it says it will accept "TV" or "NTSC" input. It it doesn't explicitly say that it will, it won't. I had good results recently at work using a couple of "headrest" LCD displays made for mounting behind your seat so the kids can watch DVD's; the 7 inchers ran about $70 via Amazon and worked great, but they require 12V at about 200 mA. I don't think their power supplies are very efficient, but it doesn't matter if they are being powered by the car or (in my case) AC mains.

CassLan

So it seems there are 2 ways I can go forward with this:

(1) pick up the MM with rs232 output, get it talking to the prop and having the prop display information..then replace the onboard lcd with the 3.0" lcd from Brilldea and use that as the primary display being driven by the prop, the upshot is that it may already have a rubber coating and already has battery holders...and probe inputs.

(2) Get that ADC circuit working on a prop, displaying information to the Brilldea lcd, and then cram that into a small project box

I may try both ways and see which ends up better. In truth, I'll probably make several of these and having the extra features of the real MM might make up for the additional $42 cost, but (I may be dreaming here) I'm hoping for something really small and thin.

I'm going to go forward with both methods and see which works out better.

Thanks for the input guys, I will follow up with progress.

@localroger- this is from Brilldea's website in reference to that LCD:

"...we have sourced a composite video driver board that mates with the LCD. That is right, attach the display to the driver board, apply power to the driver board (5.0V DC) and attach a composite video signal and you have a miniature video display. The composite video signal can be PAL or NTSC."

I'm confident this display will work, I will post results either way.

Rick

Tubular

CassLan,

Great idea replacing the screen, hadn't thought of that. I was thinking of sticking it at the back somehow.

I've ordered one of those Q1078's to pull apart and see whats possible. I've also asked the guy to measure the screen on the diagonal, I'll report back shortly. Better order a Brilldea screen, I was hanging out for the 3.5", but this gives me an excuse to use the smaller one.

Small and thin would be great but in my experience these things bulk up really quickly. I'm guessing you'll end up with a case as large or larger than the dmm

tubular

Coley

CassLan,

I'm very interested inthis tool as I too install CCTV and was looking for something similar for all my technicians.
The nearest thing I have found so far which is really useful but quite expensive is this....
www.psimagazine.co.uk/tests/cctvtests/act_rapport2.pdf

My idea was to have text superimposed onto the incoming video signal for checking video levels and so on and switched to a different mode to act as a test pattern generator.

Coley

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CassLan

@tubular- I will get to ordering as well [noparse];)[/noparse]· I wonder if that DMM will send units or it will just send numbers, it would be nice for the prop to be able to display the units as well...maybe some graphics based on what it was measuring.

@Coley- nice find! with the recent video overlay thread that doesn't seem too far from reality! (http://forums.parallax.com/forums/default.aspx?f=25&m=348906). I'm hoping I can get this done for under $100.
That reminds me of a gameboy advance. I hadn't thought about a clamshell design. I will make updates to this thread as they develop.

Rick

Post Edited (CassLan) : 5/8/2009 12:34:51 PM GMT

localroger

Ah, I had missed that they got that driver board. That will indeed work for you. Lots of forum I haven't got around to reading yet, dangit.

kwinn

Here is a simple circuit to measure both AC and DC voltages. I am assuming that any AC voltage will be 60Hz derived from the power lines. The resistor and capacitor values will vary depending on what maximum input voltage you want to measure. In my case R1/R3 were 22K and R2/R4 were 2K2. The capacitors were all 0.1uF except C3 which was 4.7uF. The signal going to the prop pin is a logic level, with high indicating AC input. In the case of AC input the reading from the ADC was multiplied by 1.4.

johnfl68

There is also this unit from Ideal (not wanting to take away from you Prop fun, but just FYI):

www.idealindustries.com/media/pdfs/products/brochures/p-2755_securitest_brochure.pdf

John

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Post Edited (johnfl68) : 5/8/2009 9:18:54 PM GMT

Tubular

@rick, the data stream from the dmm sends all the lcd segments, so you can deduce the units depending on whether the mA, A, mV, V or Hz segment is lit up. The scaling is determined by which decimal point is lit up.

Timothy D. Swieter

I had missed this thread, thank for highlighting it to me Tubular.

The display that we sell on Brilldea is a 3.0" LCD display with a driver board that accepts NTSC or PAL video inputs. I have attached inputs from the Propeller generating video as well as from the a couple CCD/mini-cameras that I picked up in the electronics market. I don't see a reason why one couldn't attach other CCTV to them, as the driver board accepts 5V DC and NTSC/PAL video signals.

At the moment I am traveling so I can't ship any units out, but I have plenty in stock and can start shipping around May 19th. Just drop me a note and I can let you know when I reenable the ordering for this screen (probably the weekend of May 16).

You got a great idea going CassLan!

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Timothy D. Swieter, E.I.
www.brilldea.com - Prop Blade, LED Painter, RGB LEDs, 3.0" LCD Composite video display, eProto for SunSPOT
www.tdswieter.com

Tubular

Rick,

Here's a photo of the back of the Q1078. You could almost fit a uOled96-prop in the 9v battery cavity, but obviously you want video capabilities.

Where the battey goes has the most room, perhaps 15mm ish of depth.

tubular