Inexpensive way to control devices from a PC?

I need to control a few devices (attached to appliance modules) from a PC. I need to be able to send commands using custom scripts/programs that I am writing or have already written, so I need something that has an app that I can call from a command line.

What is the best and least expensive hardware to use for this? I was originally thinking X10/Insteon, but the USB interfaces seem to be almost $100. For that price, I might as well do Zwave.

What PC interface (preferably USB, but I'd consider RS232) would you use and why? I don't mind paying a little extra for it if I can reuse it down the road if/when I implement automated lighting.

If you can live with X10, then you can use WebControl to send X10 RF commands to control those devices. WebControl allows you to use web browser to send X10 commands from your PC, locally or remote.

there is over 10,000 ways I can think of to do that... all are under $5 to make.
depends on voltage (ac/dc), current (amps)

What are you trying to control? Will it be plugged into the computer directly or do you want it networked? How many things are you controlling?

fwd03 said:

If you can live with X10, then you can use WebControl to send X10 RF commands to control those devices. WebControl allows you to use web browser to send X10 commands from your PC, locally or remote.

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I'm really looking for a hardware recommendation (preferably usb) that has either a well-documented API or a command-line executable. X10 is OK, if it's cheap.

I'm really looking for a

NewZealandHome said:

there is over 10,000 ways I can think of to do that... all are under $5 to make.
depends on voltage (ac/dc), current (amps)

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Care to offer any more detail? I want to control several PC monitors in a different part of the house. I planned to plug them each into a X10/Insteon/Zwave appliance module and then send the on/off commands to the appliance module from the PC in the basement. The only super-cheap way I can think of to do this is to wire a couple of X10 powerflash modules to a few pins on the parallel or serial port...but I am looking for something a little more extensible.

Lou Apo said:

What are you trying to control? Will it be plugged into the computer directly or do you want it networked? How many things are you controlling?

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Sorry, I should have been more clear. I am controlling AC appliances (in this case, computer monitors) in another room in the house. As I described above, I plan on plugging them into appliance modules and then I want the computer to control the appliance modules. I want to be able to control at least 4 or 5 of them.

Why use X10/Insteon/Zwave modules at all? I bought a used APC power strip (PDU) and web control box for under $150 total that has a web interface on ebay to control items in my AV rack. Assuming since these are computer monitors there is network nearby... Supports HTTP/Telnet/SNMP...

Would a ZigBee, perhaps an arduino, and a powertail work?

I've had good experiences with arduino and powertail combos, but have only read about using ZigBees.

may go past your pricepoint

As mentioned, a cai webcontrol would do the trick. $35 for the unit, plus you'll need a bank of relays. You can pick up a strip of 8 relays for about $20 on ebay (make sure you get ttl relays) but you'll need to wire them up to plugs and stuff which will cost a few more dollars and take time. If you want it all pre-made, do what Wuench suggested, but it costs more. CAI webcontrol is a nifty little versatile network enabled device with built-in programming logic for pretty cheap.

if it was me, I would use a usb to rs485 chip, which costs $1. this gives you up to 4000ft allowable length - then at the other end an rs485 relay to do the switching, about $5. run a pair of twisted wires or cat5 twisted wire. if you only need transistor level voltage switching then it only costs about 3cents.

rs485 gives you about switching signal speed of 10mbit per second full duplex these days.

what voltage and current are your appliances you want to switch? for 5volts it costs 3cents, for 110volts costs $10, for 240v costs $15. higher current also costs more. If you want solid state switching then its about $8, if you want super fast solid state switching then its about $15 per relay (100+ times per second on off).

Given the application of computer monitors, I'd between two options... one is something like a DigitalLoggers Web Power Switch if the devices are together, or getting into some sort of scada related relay; it's easy to switch power.

That said, specifically for computer monitors, I wouldn't go that route... I would use monitors that have super-low standby power and I'd find a way to make the PC's connected to them trigger standby mode. There are plenty of windows apps you can trigger to do this; you didn't specify what's connected to the monitors.

tadr said:

What is the best and least expensive hardware to use for this?

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These two things are generally mutually exclusive. ;-)

Least expensive is probably an X10 firecracker and transceiver- http://www.x10.com/automation/ck18a_s_ps32.html, for example. You can probably find someone on here who will sell you the firecracker and transceiver for less (maybe even me ;-), and appliance modules are pretty plentiful and cheap. There is free SW that will let you drive the firecracker.

Insteon honestly seems the most extensible and affordable combination IMO.

On ebay you can pick up USB or serial insteon controllers for less than $50.

They've recently been clearing some of their icon appliance modules (essentially a relay that interrupts a single 3 prong outlet) for $19 each.

It will be hard to find a combination of verified protocol and vast future expandability that beats this price.


Insteon is not perfect. i have it in my home and it took some fiddling, but I really like it now. The modules are fairly cheap, and have a good number of features. I use it not only to automate lighting but also to turn energy vampires off at night and when I'm gone. Since my insteon setup links with my Elk security and automation panel it knows when I'm sleeping, gone, or arriving home and issues commands to turn off or on non-essential appliances. The energy savings is modest, but since I have the system here for my convenience anyway it might as well do something to try and earn its keep.

Hard to beat this:

http://www.ebay.com/itm/APC-AP7900-SWITCHED-RACK-PDU-POWER-DISTRIBUTION-STRIP-/230772729729?pt=LH_DefaultDomain_0&hash=item35bb206781

While true - that's a great unit, that's $150 for a used one - I still think this one wins: http://www.digital-loggers.com/lpc.html it's designed for remote control and scripting.

Whoa man that one is cool. If someone were wiring their house properly ahead of time and wanted to do a centralized switching setup for their lights and outlets a device like this could nearly be used. Not ideal if the budget were higher (no dimming), but that's a lot of switchable outlets for the price!