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PRODUCTS
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Teleo Network |
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| Detailed description of the Teleo Network: |
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Overview |
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TELEO NETWORK |
The Teleo Network supplies power to all the modules in a Teleo System and carries data between modules with only four wires:
Signal Color Function V+ Red Provides power to the modules. Voltage and current capacity are determined by the power supply selected. Data A White Bidirectional Data Lines Data B Blue Ground Black Provides ground to all modules. The underlying technology used for actual data transmission is RS-485. This is a very well established technology that has been in use for many years and is most commonly used in 10 and 100BaseT Ethernet wiring.
RS-485 is a very robust data transmission system. Many signalling systems rely on the presence or absence of voltages to signal data. This is an excellent mechanism for small scale data transmission, but suffers greatly from interference when the required transmission distances get larger. By contrast, RS-485 relies on the relative voltages of two different lines to determine the transmitted data. What this means is that even in the presence of noise when the voltages on the transmission lines are being heavily influenced by outside sources, signals can still get through since the interference effects both lines and their voltages relative to each other are still preserved. If line A is a few volts above line B at the transmitter, even if the voltages on both lines are increased, the difference is preserved and the receiver can still make out the data.
On Teleo Network cables there is exactly one header (left) and one or more receptacles (usually red or orange, on the right).
Teleo Network Header and Receptacle The header is usually at one end of the cable and the receptacles are spaced out as the application requires on the rest.
Possible Teleo Network Cable Configuration Data flows in and out of all the connectors, but the header alone supplies power to the network and receptacles supply power to connected modules. This arrangement ensures that there is never more than one power supply connected to the network.
A Teleo Network originates with a Teleo Intro Module. If the Intro Module is being used by itself, the power supply can be connected directly to the Intro Module. If more modules are required, the power supply should be placed directly onto the network cable, leaving the remaining three connectors for modules (one of which must necessarily be an Intro Module). Several network cables can be daisy-chained together to create larger Teleo networks.
Teleo Network with Power Supply connected directly.
All the modules of a Teleo system are connected to the Teleo Network. There is facility for simultaneously addressing 63 modules in a Teleo system. They communicate by sending addressed packets of data to each other. Any module may send a message at any time, there is no master module which directs all network traffic.
Modules may draw their power from the Teleo Network or, if required, may draw power from other sources. This is important when the module demands more power than the network, running off the original power supply, can provide.
All active modules have a push button and an LED for basic interaction with the user as described in the UI section of the Teleo Module document.
Power to a Teleo network should be clean DC. Some cheap wall-mounted power supplies produce very noisy or only partially rectified power - avoid these. Possible remedies for noisy supplies include using a large filter capacitor. Good results can be obtained from desktop switchmode power supplies, larger linear supplies, and batteries.
The voltage applied to the network should not exceed 30 Volts - some of the components (input capacitors, voltage regulators, etc.) have absolute rated limits of 35V - 40V so it is wise to stay well within their upper limits. One thing to be careful of is that unregulated power supplies can sometimes have significantly higher unloaded voltages than they claim to have under full load. A 24V transformer, for example, might have a lightly loaded voltage of 34V or more which would be too high for the Teleo Network. It pays to check. Ideally, a regulated power supply should be used, since they have special circuitry that keeps the supplied voltage at it's specified level.
Network voltage should not fall below 7.5 Volts as this is the minimum voltage required by the on-board voltage regulators to produce the 5V the module electronics need. Watch the voltage carefully when running high current devices - sometimes they can drop the system voltage dramatically. Also be aware that long runs of cable can have significant resistance and can therefore drop the network voltage when currents go up.
Care must be taken to ensure that all the devices being powered from the network can actually function safely with the voltage being provided - a 12V light bulb which worked fine on a 12V power supply will most likely burn-out if the power supply voltage is increased to 24V. Sometimes a device rated at a lower voltage than the power supply can be run via a PWM output (from the Teleo Multi IO Module, for example) running at a low duty cycle. For example, a motor rated at 6V can be run on a 12V Teleo Network by a PWM provided the duty cycle does not exceed 50%, since 50% of 12V is 6V, the device's limit. But this is a risky practice, since any accidentally supplied higher duty cycle may destroy the device.
The maximum permissible current for the Teleo Network is 10 Amps. This is ample for most applications, but it is deceptively easy to create Teleo systems that consume large amounts of current. It is important to never exceed the 10A limit, the polyswitch on the power module will break the circuit if too much current is drawn, but modules and or cables may still be damaged.
To show how this can happen, consider the Teleo Digital Out module. This module has 12 separate 2 Amp switches. If each of these were switched on and their loads consumed their full 2 Amps, the current required would be more than 24 Amps - easily exceeding the maximum network limits. Where this kind of current consumption is necessary, the modules that can handle high currents have a means to use external power to supplement the basic Teleo Network power. This option is covered in detail in the module's respective User Guides, but the general idea is that the ground of the auxiliary power supply is connected to the module's ground and the positive side to the loads being switched. When current flows, it only flows through the load and switch, not through the whole network.
In general, high current systems should be treated with a great deal of respect. It is very easy for a dangling wire or misplaced screwdriver to connect a module's sensitive electronics to high voltages and high current sources. It's also easy to do a lot of damage by accidentally pushing a connector on the wrong way. So be careful!
Under ideal conditions, the Teleo Network can transmit up to a thousand reliable addressed messages per second. Under less ideal conditions, the rate can drop to a fraction of this.
The Teleo Network runs at 250kb/s (256,000 bits of information per second). Since there are 10bits per byte sent, this is equivalent to 25,600 bytes per second. This figure would indicate that one might expect to be able to send just over 25 thousand numbers around the network each second.
Unfortunately, the network has a lot more to do than to purely send the data. At the most basic level, each time one module needs to communicate with another, it packages up the content of the communication into one or more groups - called Packets. Each packet has a destination address, some identification information, a data size, the data itself and a check sum to ensure that the packet isn't corrupted on-route. In order for the sender to know that the receiver has actually got the packet, when the receiver gets a good packet, it sends a special packet back to the sender acknowledging its receipt. All this uses up valuable network time, but it's the price that has to be paid for reliable messages.
When there are two or more modules on the network, they may seek to transmit at exactly the same time. This is called a collision and both messages are usually messed-up. The senders can often detect when this has happened so they know to stop transmitting. They wait for a little while and try again. When this happens a lot, there is a lot of retransmission and a lot of wasted time.
So, getting back to ideal and non-ideal, the most ideal circumstances for efficient communications are when there is only light network traffic. Or if there is a lot of data arising from the system, that it comes from only one source (so there are few collisions).
The Teleo Network is very tolerant of different kinds of topology. With the exception of networks involving very long runs, almost any configuration will work. This is supported in Teleo since any unused receptacle can be used to connect an additional segment of Teleo Network cable.
Linear Configuration
Cross Configuration
Multiple Arms When particularly long networks are being considered, best communication results will be obtained by ensuring that a linear configuration is used. In addition, the far end of a long cable run must be terminated. In fact, long runs need to be terminated on both ends of the cable, but Teleo networks have a network terminator built into the Intro Module, so you only have to deal with it on the far end.
Long Linear Network with Terminator Termination on the far end of a network is achieved by a Network Terminator, which as you can see below is a header with a 120 Ohm resistor connecting the two data lines.
Network Terminator Under ideal conditions, RS-485 networks running at 250kb/s, as the Teleo network does can be expected to communicate over distances greater than 1000'.
Watch out for voltage drops over long cable lengths. The 22 gauge plenum wire we use has a resistance of around 16
/1000'. Let's say you're designing something that requires a 100' run of cable. 1.6
As mentioned above, it is recommended when considering creating a device with long network runs to use a linear topology and to terminate the network at the far end (the near end being terminated by a resistor on the power module).
Once you have considered all these things, test the setup in an environment as close as possible to the final one to make sure it works well.
Procedure for Changing Addresses
Each Teleo Module has a unique address on the Teleo Network . Each module is shipped with a preset default address, that is identical to its type. Thus, a network consisting of different modules (e.g. a Teleo Intro Module, a Teleo Digital Out, a Teleo Servo module, and a Teleo MultiIO module) will have no address conflicts, and the user will never need to change these addresses. However, if an application requires two or more modules of the same type (e.g. two Teleo Motor Controller modules), then the address of one of the modules must be changed so they can be differentiated by whatever software is controlling the network. A module's address must be unique on the network - no two modules regardless of type should share a common address.
Teleo Default Module Addresses
Introductory Module 2 Multi IO Module 3
Stepper Motor Module 4 Servo Module 5 Motor Controller 2x2A 6 Digital Out 8 Video Module 9 Analog In Module 10 When a module's address is changed, the new address is recorded in the module's permanent memory so that it is not forgotten when the power is removed. This has the desirable effect of ensuring that each time the power comes up, the right messages get to the right modules.
The basic procedure to change a module's address is the same regardless of the software being used:
- with the power on
- select the module that you wish to change the address of
- hold that module's push button for three seconds
- the LED will glow half bright
- button press messages will be sent out from the module
- after about three seconds, the LED will start to flicker slightly
- release the button
- now the module is ready to have its address changed
- if you change your mind, you can deactivate this mode by pressing the module button again
- request the software you're using to send an address change message
- only the module with the flashing LED will update its address
- the module will now send and receive messages from the new address
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