ANR - Advanced

Optically Coupled Bicore (OCB)

OCB Picture


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Introduction

Imagine a simple bicore -- two neurons connected together in a loop. Now break open the loop at one point and insert an infrared transmitter on the output side of the break and an infrared receiver on the input side of the break. That's the most basic form of the Optically Coupled Bicore, or OCB.

Basic OCB The first question that comes to mind with this circuit is, "What can you do with it?" The most obvious application is to use it as a simple detector. As long as the optical path is unobstructed, the bicore will run. As soon as something interupts the path, the bicore stops running.

The second question that comes to mind is, "Why use a bicore at all?" It's a good point; all that's needed to detect an object is the transmitter and receiver. The advantage of using a bicore is that a typical infrared (IR) emitter draws quite a bit of current. By using an assymetric bicore running at a moderately high speed, the transmitter can be turned on very briefly, but remain off for most of the time.

Clearly the circuit is just a little too simple. There are two obvious problems with it. First, if the optical path has been interupted, the bicore will not automatically start again once the path is restored. Second, the only indication that the path is complete is when the bicore is running -- and no matter where we monitor the circuit, we will always get a pulsing output, not a steady signal. Additional circuitry is required to deal with these issues.

A final concern is with the IR transmitter and receiver. How complicated are they? Are the parts easy to acquire? How big are they, and how much do they cost? For the purposes of this initial design, I've attempted to use simple, inexpensive parts which are available through a reliable mail order outfit.

Configurations

Remote OCB The basic circuit has a number of possible applications which go beyond a simple object detector. By simply placing the transmitter and receiver beside each other, both pointing in the same direction, a whole new set of possibilities come to light.

Infrared light is reflected by most common materials, so this new configuration can be used as a proximity detector. Depending on the emitter intensity and the physical arrangement, surfaces can be detected from a distance of 25 mm to 100 mm (1 to 4 inches). Shiny metal surfaces can be detected at even greater distances.

Furthermore, due to tiny irregularities in many surfaces, there is scattering of the IR light. This is sufficient to allow the circuit to detect surfaces that are at an angle to the light path. This same effect can also be used to set a precise detection distance. By using a narrow beam transmitter and restricting the receiver beam width, the two devices can be placed at a slight angle so they both focus on a specific point. This arrangement will respond only when the focus point strikes a surface.

Finally, even more possibilities occur when two identical remote-sensing OCB circuits are used. When the two circuits are pointed directly at each other, the effect is to create an optically coupled microcore.

Remote OCB Second Remote OCB This arrangement can be used in a variety of ways. Two robots can detect each other and respond in some way. Or a stationary beacon can signal its location to one or more robots. There is also the possibility of transmitting information by sending various numbers of pulses, and counting them at the receiver.

Circuit Elements

There are five basic modules to this circuit. If you have built a microcore or a bicore and are interested in remote proximity detection or communication between robots, I encourage you to try building this circuit. It is a good idea to build and test each module in the order shown. You'll find assembly and test instructions each page.
  1. The IR transmitter.
  2. The IR receiver.
  3. The basic OCB circuit.
  4. A signal injector to restart the circuit after the optical path is interupted.
  5. An output generator to send a continuous signal when the bicore is running.

Finally, a complete diagram is provided, along with some suggested variations and a parts list is also provided.

Before progressing too far with the circuit you may want to check out the improvements page. I'll be posting improvements and minor changes here as I (or you) discover them.

If you experience difficulties with your circuit, get in touch with me and I'll do what I can to help solve the problem.


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© 2000 Bruce N. Robinson. Last updated 2000-12-22.