ops: :? my mistake, resolution is too advanced for me. All I am using is about 32 phototransistors and did not want to use demultiplexer to get one switch at a time. I think I have almost a solution. I am not gonna use a microcontroller, but 4 parallel to serial shift registers. The MSCOMM control in vb allows me to specify the lenght of the word so I should be fine. The only thing now is how to wire all of them together. As I said research always helps only here I have been reading the computer nonstop for the past 10 hours. Will see what I can do about it. I hope I wont burn any chips. One more question though. How long can the serial cables be without amplifying and can I make my own serial cable lets say from the regular hookup wire?

__________________
If we never asked stupid questions, we would be a planetfull of geniuses

 

Vopap,
If you are going to use serial data to communicate with your PC, then you will need start and stop bits added to each byte of data. So it's best to let the controller handle that. Ideally, the uC should read out data one bit at a time from a register. In that case, it means less programming if the uC took in sensor data a byte wide instead of serially.

Just a thought. If your sensors are phototransistors (I assume just C and E connections) then presumably they are either on of off. You could do an 8 x 4 matrix like you would for a keypad entry, with 8 input lines and 4 output lines. Put a diode in series with each PT for isolation and put each of them across one of the 32 intersections of the matrix. Then lifting each output line in turn and checking the status of the 8 input lines will check all 32 sensors and give the results in 4 bytes. So no extra chips would be needed. Magic!

RE: your last line asking whether you should do electronics, or programming or modelling first. I think you should plan first, and decide just what you want to achieve and the various ways of doing it, before you go into detail about what chips you will use. You have mentioned the sensors. How about these:

1. How about data/insructions coming from the PC?
2. Are any sensor inputs to be actioned automatically by your robot -
like maintaining depth and speed?
3. Are PC instructions to have priority?
4. What other activities does the uC do?

Regarding the type of cable. I think 3core 2A mains flex would do. The thick protective outer sheath would keep the water some distance from the conductors and that will reduce capacity. As for how long can the cable be, it will depend on the data rate you use because the capacity of the cable will increase with length and that is what determines rise time, and that, in turn, determines maximum data rate. I've used 60ft of 3core at 1200bps, but that is certainly not its limit.

 

the universe collapsed, all my research has done nothing: I cannot use infrared detectors under water. Do you know how to interface sonar or ultrasonar transducers to the oopic?
I know I have too amny questions :cry:

__________________
If we never asked stupid questions, we would be a planetfull of geniuses

 

I would have thought you need to send a short, sharp pulse to the tx transducer and then time how long it takes to receive the echo from wherever.

You know, you would get far more help, more quickly, if you set out clearly what you are trying to do, instead of just asking questions, piecemeal.

What are you trying to measure?

 

sorry, I thought my questions had only one side to them. OK, what I am trying to do is find out the distance to the bottom of the river ( I thought the that is the only use of sonars beside comunication, obviously I was wrong).
So do you have any sugestions. Oh if I missed any other info, ITS A TETHERED SUBMRINE, controlled by the submarine by a serial port from the pc with a USB camera. I hope that fills in all the holes in the question

__________________
If we never asked stupid questions, we would be a planetfull of geniuses

 

Not really. You haven't said why you needed 32 sensors. Or if the depth information supplied by the sonar is to be automatically dealt with by the tethered sub itself, or by the controlling sub, or handled by you with a control stick at the PC.

In other words, I cannot see the overall picture.

 

ops: :cry:
So what happened I was first gonna use infrared detectors (a great variety of them around 32 all around the ship) I also mistakengly thought that infrared gives a digital output. Now I found that IR phototransistors are analog output an that they do not work in water, so my 32 phototransistors flew out of the window.

To satisfy myself with some other sensors, I decided to use one sonic meter to measure to distance to the bottom of the river. So now I do not need any 32 bits of data for the sensors but less.


Now my electrical design is so far:

1. Use a OOPic Microcontroller.

2. OOPic has TTL circuits, they are being converted onboard into CMOS of the computer by a IC like SN75188 or the MAX203.

3. Connected to the microcontroller, I have:

OUTPUT FROM THE OOPIC
a. 4 H-bridges for each pump to enable the sub go up or down i.e. change its buyancy.
b. Another H-bridge for the propultion motor.
c. Servo control (one line) for the controll of the ruder.
d. ???Some circuit (probably another H-bridge till I find something more apropiate) to control the on/off of a lamp to iluminate the path underwater.

INPUT TO THE OOPIC
a. double-axis tilt sensor (one of the ANALOG products). Two digital lines (PWM), plus self-test line
b. sonar meter to measure the distance to the bottom of the river (this circuit is something I have to find.

4.Totally independent from the microcontroller, I have a webcam, connected straight to the computer via USB port. Mounted on the front of the sub. Gonna use it to take pictures and know where I am going.

5. Ideally, this should be made remote control, however there must be a two receivers and two transmitters on the sub and connected to the computer (serial output transmitter, usb output transmitter, serial input receiver and usb input receiver) I believe it would be possible to interface the OOPic to the usb output of webcam and so reduce the number of receiver-transmitter pairs, however, I would need about ~6mb/s transmittion for the camera, plus I would have to play around with the webcam driver i guess to be able to interpret the data. So for now, my solution is to make the robot tethered

6. Since the robot is tethered, I will a have power supply outside, something like an old car battery (probably will have to reduce the power for the servo, transformer wont work so I better find a servo with 10 v of voltage suply)

7. The frame is made of PVC, sealed hermetically but with possible access inside to acomplish required changes (hopefully none)

8. I would make my own PC program to control the robot, and hopefully with a screen in it showing the output from the camera

So I have two questions:

1. URGENT. How can I interface the transducers to the OOPic to measure the distance to the botom of the lake. Analog or PWM output would be perfect. If you can give me the circuit, that would be exceptional
2. Optional, but a nice thing to have: How can I make the thing wireless (In here I am very dumb: how to interface the usb to pic? how to make the wireless transmission to the receiver/transmitter on shore? How to isolate the camera output so I can use camera drivers on the PC?) This is closer to science fiction :cry:



Hope that is enough info pebe :? ops:

__________________
If we never asked stupid questions, we would be a planetfull of geniuses

 

Yes, that's a very good description.

I have never designed or built a circuit for a depth sounder, but I believe they use a ceramic disc with a resonant frequency of about 150KHz. A transmitter hits the disc with a single high power pulse which sends a sonic signal to the seabed and is reflected. The returned pulse is picked up, amplified, detected, and compared in time with the transmitted pulse. The distance is calculated from the elapsed time.

I have searched for suitable circuits on google but without much success. These are the only ones which may be relevant.

http://www.riccibitti.com/sonar.htm.
http://groups.yahoo.com/group/aus-el...cs/messages/74

It may be that you may have to purchase a used one.

About the radio link. I assume you intend to have some sort of floating station with cable from your sub to the station and radio link(s) from there.

It seems you only want to send data one way - from your PC. That should be fairly easy.

For the video, I wouldn't attempt to go via the controller - if the camera wants 6Mbs then most controllers won't be able to handle it. I think it better to take the output from the camera as it is (USB) and modulate that straight on to a radio carrier. You can get radio links that work on 2.4GHz and so have adequate bandwidth. When received, change the demodulated levels to suit the PC USB interface.

On the question of carrying signals through the water, it would be possible to use low frequency radio to keep attenuation low, but there is no way you could bring up the video signal except through a cable.

Hope that helps a bit.