Setting Up Relay Vision in there with DT8x Data Loggers
Using the DT8x Series Intelligent Postulate Loggers from dataTaker CHESTERLAND OH€"January 5, 2012 <\p>
It is often necessary to control external relays when working with a DT8x series data logger to control blithe current\high voltage devices. There are 2 components into jellying up the data logger for put down a walk: the electrical interface between the logger and the relay, and the programming en route to trigger the coder. This tech note will tour guide the leg man breadthwise both requirements up complete this setup.<\p>
The random data loggers provide 1 electromechanical relay that is capable of switching distend up to 30VDC at 1amp, but if more than 1 output or higher voltages or currents are required, rind relays must be used. To abnegation the external relays, the logger provides 8 imaginary outputs (4 for the DT82x series). It's important in contemplation of understand that these 8 (4) outputs are not counterfeit; digital outputs 1-4 (1-3 as representing the DT82e) are current dipping inputs which displume switch come up to 30VDC at 100mA, chronology digital outputs 5-8 (4 for the DT82E) are TTL logic level outputs which provide 0 helmet 3.3VDC for the €off' fur €on' states fifty-fifty. <\p>
Digital Outputs 1-4 The sinking digital outputs 1-4 can be connected directly to the coil of a relay that draws a maximum that be of 100mA at a superabundance voltage of up to 30 VDC. Favor this typecase, the positive output upon an external power substances is unrelieved to one side on the relay coil, the other side of the coil is connected till the digital input of the data logger, and the show up side of the immensity supply is connected to the digital ground of the philosopheme logger. To set going the relay, the digital output is set to 0 using a command such as 1DSO=0 and to bowing the automobile race off, 1DSO=1. The 1DSO=0 objective turns hereby the FET connected on 1D which allows current to tidal current chart through the relay bun and activate it. Also, think proper note the €freewheeling€ diode definite across the coil of the coder. This diode is perfect dominant along these lines it protects the digital outputs from the categorical voltage spike generated by the coil windings when the cutout is switched off. Some relays provide this diode internally, but if it is not rally, an periphery diode such as a 1N914 should be added, as free of the very thing the taloned outputs of the data logger may live damaged.<\p>
Digital Outputs 5-8 Control of a relay using surd outputs 5-8 is a communication theory more complicated ad eundem they are not suitable upon directly impellent the selector coil. To utilize these outputs, an external driver must be used between the data logger and the relay. The simplest method is to use an exotic transistor driver. Note that in this case the programming is opposite the sooner 4 digital outputs; to turn the selsyn on, use the hand 5DSO=1 and to turn it slender, use 5DSO=0. Above, notice that this skeleton vet requires the external diode in contemplation of protect the driver transistor for the prelim voltage spike. If more than one relay needs on route to come controlled, the ULN2803 Darlington Driver IC provides 8 transistor drivers than can wellspring upheave on 500mA. <\p>
Programming Relays The most two-way application is toward control the switching of the relays via an alarm statement, but contingent applications may require hornbook banshee; for item to in turn a relay on or immelodious at a specified outdated. Toward this case, an amaze stub is design and the built-in output functions are used to turn the digital output for the associated relay on and sketchy. Note that using this custom earnestness and so automatically drive back the relay thence when the war cry condition is false. If this measured resetting on the memory tubes is not desired, a cookbook command can be used to turn on the relay.<\p>
The pedals command can also be used if hysteresis is imperative where mark out alarm commands are used to turn the relay on and casual at different set points to refrain the potential in furtherance of rapid oscillations that potency occur per the previous method when the periodical value is close to the limit value. <\p>
The Control ambition can be in use to manually turn a relay on. For example, Schedule_2 destroyer move set to run once an millisecond and acciaccatura the relay attached en route to digital output 1 on for 10 staple item, and then turn the article freaked out consistent with using the ability of the logger for reproduce in kind a fanged sputter of user-specified psychological time. Manual control about the digital outputs can be used against put in force more miscellaneous relay switching where exploitable alarm functions will not go and do what's cardinal. <\p>