I must say I’ve been surprised by the calls and emails regarding the construction of custom gear, beginning with Buc Fitch’s German-made KEO audio amplifier module in the previous issue.
Fig. 1: The Velleman K8015 is a multifunction relay kit with adjustable delay.
Fig. 2: The K8042 is a symmetric or bipolar power supply. Wayne Kirkwood shares some time-saving kits from Velleman. Though we could design and build these widgets ourselves, many of us simply do not have the time.
One kit Wayne found useful is the Velleman K8015 Multifunction Relay Switch. We’ve all had the need for 555-based time delay relays. The K8015 is an “off-the-shelf” kit using a PICmicro — Peripheral Interface Controller, trademarked by Microchip Technology — married to a power relay with a trigger input. See Fig. 1.
Using a four-position DIP switch, the timer can be configured to operate in 15 modes. Some modes provide two delays. Rather than use the tedious process of setting a trim pot on a 555 — which is difficult for long delays — the K8015 has a learning mode in which the delay time is recorded by button presses and stored in non-volatile memory.
The delays can be as short as 2 seconds to as long as 12 days. Wayne says the K8015’s “blinking” mode is ideal for on-air warning lights. With the addition of a coupling capacitor on the trigger input, a tachometer signal can be used to sense loss of rotation or air flow.
Amazon has the kit available for under $30; type “Velleman K8015” in the Amazon search block.
The useful kits continue. How many times have you needed a simple split audio supply? The Velleman K8042 is a complete “symmetric” (split) supply using the popular LM317/LM337 regulators. Though it’s designed for split secondary or center-tapped transformers, it can be used in a half-wave configuration to run from an AC wall-wart.
Fig. 3 Velleman’s VM201 Ethernet relay card can be controlled by a smartphone. Search for Velleman K8042 in the Amazon search block. Wayne writes that the K8042 is something of a secret since searches for “split” or “bipolar” power supplies do not index to the “symmetric” K8042.
Another forward-thinking product from Velleman, the VM201 Ethernet Relay card, is ideal for remote control applications. The relays can be operated via a smart phone or web interface or under timer control. There is also a single status input. Wayne hasn’t tried the VM201 but he has used the K8015 and K8042.
Wayne suggests turning to Velleman’s site when you need a simple widget to solve a problem. You may find something readily available that will save you lots of time. In addition to Amazon, Velleman products are distributed by mail-order dealers such as Jameco, Fry’s and Micro Center, as well as smaller local electronics shops.
While we’re on the topic of kit solutions, let me tell you about network staff engineer Steve Tuzeneu and his dilemma.
Fig. 4: LeaningTech manufactures this inexpensive FM stereo receiver module. Now that Dayton Industrial no longer makes receivers to use with EAS units, Steve found a little radio that just might do the job.
The LeaningTech DSP and PLL Digital Stereo FM Radio Receiver Module with serial control costs just $14.32 on Amazon and features an LCD display with very low power consumption. The module is seen in Fig. 4.
For use as an EAS receiver, the specs say there is an automatic memory of data prior to a power failure, so you’re not resetting the tuning should the power die. It appears to be a neat project for an engineer searching for a cost-effective receiver. If you try one, let me know how it works.
Search Amazon for “leaningtech fm002.” Also, you can watch a four-minute YouTube video that describes its operation at http://tinyurl.com/rw-fm002.
Contribute to Workbench. You’ll help your fellow engineers and qualify for SBE recertification credit. Send Workbench tips to [email protected]. Fax to (603) 472-4944.
Author John Bisset has spent 46 years in the broadcasting industry and is still learning.
He handles West Coast sales for the Telos Alliance. He is SBE certified and is a past recipient of the SBE’s Educator of the Year Award.