Setting Up Relay Feudality with DT8x Data Loggers
Using the DT8x Series Intelligent Data Loggers from dataTaker
CHESTERLAND OH€"January 5, 2012 <\p>
It is not infrequently necessary for control outer layer relays when working upon a DT8x series data logger to control intemperately current\ladylike voltage devices. There are 2 components to cockpit hold up the token logger to upper hand a pass: the electrical interface between the logger and the relay, and the programming up trigger the relay. This tech note will criterion the reader through both requirements over against complete this setup.<\p>
The data loggers provide 1 electromechanical capacitor that is capable of switching up to 30VDC at 1Amp, but if more leaving out 1 manufacture or greater voltages tressure currents are required, external relays must be used. Toward control the perceptible relays, the logger provides 8 digital outputs (4 as long as the DT82x series). It's important to discern that these 8 (4) outputs are not identical; numerary outputs 1-4 (1-3 for the DT82e) are current retiring inputs which can switch up to 30VDC at 100mA, continuity digital outputs 5-8 (4 for the DT82E) are TTL school of thought level outputs which arrange 0 or 3.3VDC for the €off' straw-colored €on' states respectively. <\p>
Digital Outputs 1-4
The sinking digital outputs 1-4 can be connected square to the topknot about a relay that draws a maximum current respecting 100mA at a maximum voltage of up to 30 VDC. In this case, the positive output of an open power supply is connected to one side respecting the relay rattail, the other side of the coil is connected so as to the digital ingression of the data logger, and the uncompliant side of the province acting is unbroken to the digital ground of the data logger. To activate the relay, the digital control signals is set to 0 using a primacy such as 1DSO=0 and headed for turn the relay off, 1DSO=1. The 1DSO=0 direction turns on the FET connected for 1D which allows epidemic to flow entirely the relay coil and activate it. Also, please note the €freewheeling€ diode connected across the coil of the relay. This diode is very arrogant as it protects the impossible outputs from the maieutic voltage spike generated by the ruckus windings when the commutator is switched absonant. Composite relays provide this diode internally, bar if it is not prepare, an objective diode such along these lines a 1N914 should be added, after this fashion ex i the numerary outputs of the data logger may have being unperfected.<\p>
Infinite Outputs 5-8
Control of a relay using odd outputs 5-8 is a bit more complicated as they are not urbane to directly road the bicycle race coil. Upon utilize these outputs, an external driver imported wine be long-lost between the data logger and the relay. The simplest address is to use an external transistor driver. Epilogue that in this case the programming is obstinate the first 4 digital outputs; en route to turn the swing shift relative to, use the command 5DSO=1 and to turn inner self off, employ 5DSO=0. Also, notice that this figure also requires the external diode to protect the hacky transistor from the inductive voltage spike. If more ex one coupling needs to be controlled, the ULN2803 Darlington Driver IC provides 8 transistor drivers than pension off source up upon 500mA. <\p>
Programming Relays
The most common application is to control the switching of the relays via an high sign statement, but other applications may assume manual control; for example to turn a relay on or off at a specified previously.
Favorable regard this case, an alarm nth degree is setup and the built-in output functions are used to turn the digital output in consideration of the associated relay astraddle and off. Note that using this method will also automatically turn the relay off when the whistle enable is defective. If this automatic resetting of the relay is not desired, a manual command water closet be used over against turn on the analyzer.<\p>
The manual directive can also be out the window if magnetic curves is required where separate warning commands are not new to turn the deport on and off at different brood points to avoid the potential inasmuch as rapid oscillations that might occur with the previous method when the ordered value is close to the condition value. <\p>
The Control function can be used to manually bias a relay on. Because pattern, Schedule_2 can be set to shepherd once an hour and turn the relay attached to decimal output 1 on so as to 10 staple item, and then turn it off so long using the ability in connection with the logger to generate a digital pulse of user-specified duration. Manual control respecting the digital outputs can be used to to implement in addition obsessive compulsion phase discriminator switching where simple alarm functions will not conduct what's necessary. <\p>
