Bluetooth Range

Bluetooth devices are not commonly chosen for their range abilities as this is limited to 200 to 300 feet depending on the antenna option but more for their ease of integration into applications.  With so many devices supporting Bluetooth communication they are a very popular wireless option.  At this time we offer two antenna options, a n integrated antenna (shown in the module to the right) with a range of approximately 200 feet and an external antenna option with a range of 300 feet.  Range estimates are under ideal conditions (Clear line of Site) with most devices.  Another factor in the actual range a user can achieve using Bluetooth devices is the sender or master device.  This could be a smart phone, tablet or computer.  All these devices will have different range abilities which will play a factor in the actual range in a given application.

Range testing can be done at your site!  We are unable to provide you with a testing board but we do offer a 30-day money-back-guarantee on single board purchases.  If you purchase a board and find that the range is not enough you can simply return it within 30 days for a full refund.  Orders shipped out of the country we will refund the purchase price for the board but not the shipping.  

Visit Relay Pros at for more on Bluetooth Relays.

Wireless Range

One of the most common questions we receive from customers is "What is the range of your wireless Products?"  Will this wireless board work under these conditions.....? They sounds like a very simple questions but there are several factors that play a part in the actual range of all wireless devices.  In this post we will discuss first the factors that play part in the actual wireless range of these boards.  In upcoming posts we will look at each wireless protocol in depth.

Several things can play a part in determining the actual range of our devices in a given environment.  These Range Obstacles as we will call them can be anything from a masonry wall to a tree.  Different materials affect range in different amounts, for instance, a wood and sheet rock wall will affect the wireless range of a device far less than a brick wall or even worse metal.  This means the actual structures in your environment will play a key role in the actual range distance you will achieve with our products.  If the user believes structures or objects could hinder the range of the devices being used in a given application then the wireless product should be over rated for the actual desired wireless range, meaning if the user is trying to achieve an actual wireless distance of 300 ft but there is a wood and plaster wall between the two devices then the user should use devices rated for 1 mile range rather than devices rated for only 300 ft range.  This is called compensation for wireless range obstacles.

Another range factor that plays a large part in actual range is the Power, Frequency, and antenna Options of the actual wireless devices being used.  National Control Devices offers a multitude of wireless options including but not limited to Bluetooth, 802.15.4, ZB ZigBee Mesh, and XSC.  These different devices operate at different Frequencies, Power Output, and Antenna Options.

Many factors play a role in the actual range these devices will achieve in a given environment or application.  The best way to determine range in a given circumstance is to field test the devices in the environment they will be implemented in.  Most wireless engineers will say that there is no better test for wireless devices than a field test so please view the videos and take all factors in this article into consideration when choosing the right product for your application.  Relay Pros offers a 30-day money back guarantee so you can field test our wireless devices at your location without wordy.

Wiring to Normally Closed Connection

With a Single Pole Double Throw (SPDT) relay the relay will have a Common, Normally Closed and Normally Open connection.  When the relay is not energized or in the off state the arm from the common is at the Normally Closed state.  When Energized the arm swings to the Normally Open side.  If you wire a light to the Normally Closed side the light will actually go off when the relay is energized.  I think of this as wiring the relay backwards so that the light goes off when the relay is energized.  On rare occasions we get an application where wiring to the Normally Closed side is required. 

We offer SPDT relays in our 5, 10 and 20 amp versions throughout or site. 

LabView Programming

We’re going to try to add programming and programming samples to our TechTip Tuesday lineup periodically.  Some may come from customers and some from NCD directly.  Here's LabView sample a customer posted to NCD’s forum.  You can download the sample at: http://www.relaypros.com/Software/83-ProXRseriescontroller.vi.  You can use just about any programming language that supports serial communications when writing your own program.  Visual Basic is probably the most popular but we get a lot of calls asking if LabView can be used. 

 

Induction Suppression

Controlling a Motor or Solenoid
Inductive loads can best be defined as anything with a magnetic coil, such as a motor, solenoid, or a transformer. Controlling an inductive load using our relay controllers requires the use of induction suppression capacitors. The purpose of this capacitor is to absorb the high voltages generated by inductive loads, blocking them from the contacts of the relay. Without this capacitor, the lifespan of the relay will be greatly reduced. Induction can be so severe that it electrically interferes with the microprocessor logic of our controllers, causing relay banks to shut themselves down unexpectedly. In the case of USB devices, customers may experience loss of communications until the device is reconnected to the USB port.

Easy to install
As you can see from the diagram above, an induction suppression capacitor is very easy to install. The capacitor should be located as close to the relay controller as possible, and is connected in parallel with the load you are trying to control. Induction suppression capacitors are NOT polarized, and may be used in either AC or DC applications.

Choosing the Right Capacitor

Choosing the correct induction suppression capacitor is simply a matter of choosing the maximum voltage requirement of the device you are trying to control. During checkout you will have the opportunity to purchase capacitors.

Resistive Loads
Unlike inductive loads, resistive loads such a incandescent lights and element heaters (without a fan), do NOT require an induction suppression capacitor, and will NOT benefit from its use.

Choosing the Proper Amperage

Relays often have two ratings: AC and DC.  These rating indicate how much power can be switched through the relays.  This does not necessarily tell you what the limits of the relay are.  For instance, a 5 Amp relay rated at 125VAC can also switch 2.5 Amps at 250VAC.  Similarly, a 5 Amp relay rated at 24VDC can switch 2.5 Amps at 48VDC, or even 10 Amps at 12VDC.

Volts x Amps = Watts - Never Exceed Watts!
An easy way to determine the limit of a relay is to multiply the rated Volts times the rated Amps.  This will give you the total watts a relay can switch.  Every relay will have two ratings: AC and DC.  You should determine the AC watts and the DC watts, and never exceed these ratings.

Example Calculations
AC Volts x AC Amps = AC Watts	DC Volts x DC Amps = DC Watts
Example: A 5-Amp Relay is Rated at 250 Volt AC 5 x 250 = 1,250 AC Watts	Example: A 5-Amp Relay is Rated at 24 Volts DC 5 x 24 = 120 DC Watts
When switching AC Devices, make sure the AC watts of the device you are switching DOES NOT exceed 1,250 when using a 5-amp relay.	If you are switching DC devices, make sure the DC watts of the device you are switching DOES NOT exceed 120 when using a 5-amp relay.

Resistive & Inductive Loads
Relays are often rated for switching resistive loads.  Inductive loads can be very hard on the contacts of a relay.  A resistive load is a device that stays electrically quiet when powered up, such as an incandescent light bulb.  An inductive load typically has a violent startup voltage or amperage requirement, such as a motor or a transformer.

Startup & Runtime Loads
Inductive loads typically require 2-3 times the runtime voltage or amperage when power is first applied to the device.  For instance, a motor rate at 5 Amps, 125 VAC will often require 10-15 amps just to get the shaft of the motor in motion.  Once in motion, the motor may consume no more than 5 amps.  When driving these types of loads, choose a relay that exceeds the initial requirement of the motor.  In this case, a 20-30 Amp relay should be used for best relay life.

Switch Using Multiple Relays

A more complex switching operation may need the use of more than one relay to perform the task.  In this case we will look at using two relays to switch a single item.  Our example will be switching an irrigation system and we have two criteria to meet before we want the water to flow.

For our example we will use a 2-channel ProXR Lite board.  This board has two relay and eight Analog to Digital inputs onboard.  We will connect sensors to the inputs and have them control the relays. 

First we have the basic need that the soil needs to be dry before we switch on the irrigation system.  We will then put a moisture sensor in the ground and connect it to input 1 on the board.  In our programming input 1 will switch relay 1 when the soil is at a certain moisture level (dry).  The second need we have is that we don’t want to irrigate in the heat of the day.  We will connect a light sensor to input 2 of our board and program it to switch relay at dusk. 

As you can see by the diagram, both relays will need to be energized to trigger the light or irrigation in our example.  The electrical signal will come into the common and when the arm of relay 1 swings to the NO side (the moisture sensor activates) it will allow the signal to now flow to the common of the second relay.  When the light sensor in our example says it’s the correct darkness it will swing the arm to the NO position on Relay 2 and allow the signal to activate the light or irrigation.

This example is for irrigation but it can be used in many different applications where your switching is controlled by multiple variants using automatic or manual mechanisms. 

To achieve this we have a couple of options available.  You can purchase a 2-channel computer controlled relay and write the program yourself.  you can find these on our site at: http://www.relaypros.com/Relay/Relay/CAT_RELAY2.  Another alternative is to purchase a Reactor Relay which operates from the sensor inpurts.  You simply configure where the trigger points will be with no programming involves.  You can find the 2-channel Reactor boards at: http://www.relaypros.com/Relay/Relay/CAT_RELAY2_REACTOR.