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Manufacturer of computer controlled relay, I/O and custom boards for commercial and industrial applications.

Please Note: Pencom will be closed from September 12th thru September 23 - we will re-open on September 26

** Please note supply chain shortage update 09-07-2022 -  a limited supply of the backordered parts will be arriving around September 28th for the USB boards - more parts are on order:   We have many backordered boards that will be produced first - notifications will go out to customers to verify the orders are still valid.

There will be production delays due the volume of the backorders

Due to the supply chain shortages we have been having a difficult time obtaining parts to produce our products.  Some of our parts have been on order for 12 months  Some parts are being received for certain products and we will do our best to fulfill what we can.

In addition we have been experiencing problems with our email system and many emails were never received on the following accounts our and, this has been happening for some time and we were unaware since it is happening sporadically. 

We have created two new accounts to use until we can determine the problems we are having with our system and please use these emails to contact us.

Other email address have been the same problems and we will work to correct these too.


8 Channel RS232 Relay Board W/IO and w/240V Power

Note: this unit is a 240VAC 50/60Hz powered unit

If daisy chaining additional boards to a unit connected to the PC - only one modular cable is required per each additional unit. Modular cables available seperately.
Typically a 2-3 Day Production <10pcs
Our quantity discounts:
Quantity 5+ 25+
Price $120.27 $113.94
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8 channel RS-232 relay board with heavy duty 10 Amp 250VAC/28VDC SPDT power relays, controlled through one of the PC RS232 serial ports.

Includes 8 channel TTL compatable input/output port individual channel selectable in setup program.

Designed for single board operation or multiple board operation on the same serial port. Up to 16 boards can be connected in a daisy chain configuration, with up to a total of 128 - 10 Amp relays under computer control.

With an on-board 240VAC 50/60Hz power transformer. (NO enclosure available).

  • ASCII commands to control relays.
  • Easy hook up using standard modular telephone cable.
  • Any software language that can write to the PC serial port can be used with this relay board NO special drivers needed.
  • 4800-38400 baud (default 9600 baud)
  • LED Indicators for relays included

Eight Channel Relay Instruction Manual (8_ch_relay_manual.pdf, 213 Kb) [Download]

8 Ch Relay Board Dimensional Drawing (8_Ch_Dimensional_Drawing.pdf, 85 Kb) [Download]

Application Note 115 - Compatibility information (app_note_115.pdf, 91 Kb) [Download]

Application Note 156 - Detailed board command information (app_note_156.pdf, 127 Kb) [Download]

The information below describes the power options, (this is the voltage that powers the board itself - not the voltage/current the relays can handle).

Choose the option that best suits your application.  Some options are available only on specific boards, and it depends on the type of control and the relay options for that board.

AC Wall Adapter - wall power supply that converts the AC voltage to DC to power the unit, the cable plugs into the unit with a DC power connector.

DC Terminal Block - Typically used when a regulated DC power supply with sufficient capability is already available where the unit will mount, or to power a daisy chained string of boards.  Includes reverse voltage protection to prevent damage to the board if the power leads were installed backwards.  Most of our boards will operate on 9-12VDC.

120V 50/60Hz - This has an on-board power supply that will operate directly off the 120VAC line voltage.  The line voltage connects to a three position terminal block on the board that is marked with L1 (Line 1 -typically black), N/L2 (Neutral wire - typically white) and GND (Electrical ground - typically green or bare).  Common practice is to add an inline fuse for safety.

240V 50/60Hz - This has an on-board power supply that will operate directly off the 240VAC line voltage.  The line voltage connects to a three position terminal block on the board that is marked with L1 (Line 1 -typically black), N/L2 (L2 - typically red, but could be another color) and GND (Electrical ground - typically green or bare).  Common practice is to add an inline fuse for safety.

Bus Power Option - This power option is only for USB boards with the Reed relays installed and specific I/O boards.  The board is powered by the USB port and must be a high power port or USB port from a powered hub with a 500mA output. 

Note: USB devices are also required to automatically enter ultra low-power suspend mode when the USB host is suspended, and this may turn off the power to the board and all relays will turn off that were active.  Nevertheless, many USB host interfaces do not cut off the power supply to USB devices when they are suspended, it depends on the host controller.  If this is a problem for your application use the USB boards that are powered by an AC adapter or DC terminal block power versions - these will not turn off the relays once set by a command (unless the power is disconnected from the board).

Daisy Chain Operation

8 Channel relay boards have the capability to daisy chain units in a string - connected to one control method (RS-232, USB, etc.) on the PC or embedded controller.  Most 8 channel boards have an RS-232 output that is used to connect additional units using only one control port. 

Up to 15 additional relay boards may be connected to the first unit - for a total of 128 relays under the control of one port.  Each board has an individual hardware address that is set on each unit by a DIP switch.  This allows control of one unit that will respond to it's address without affecting the other units on the daisy chain.  All the units are hardware connected - so each unit receives the command sent to the first board almost instantly.

The first unit connected to the PC or embedded controller can be any of the control methods available.    However each additional board connected to the daisy chain are RS-232 units, as shown in the drawing below: The RS-232 units may be up to 50 feet or more between units.

In addition, if only one or two more relays are required for your application, a 1 or 2 channel unit may be connected as the last board on the daisy chain to add the extra relays or if you need to add relays and I/O and a couple ISO ports to your application.  

1 & 2 channel units are typically connected to only one control method, however one RS-232 board may be the last board on the daisy chain - if only a couple extra relays are needed to save cost.  This board would be address "A" as this is set in firmware, and the other boards would need to be set to "B" through "P", so each board may be accessed separately.

Daisychain configurations examples