Definitive Kit 74 Thread (hopefully)

**FarmerChad** · 12-13-2010,12:24 PM

Ok, periodically questions seem to arise about the Kit 74 or the K74, which ever you want to call it. These questions popup in various forums and sometimes wind up in my inbox. I decided to write this basic tutorial in hopes of helping out anyone who may have questions about this commonly misunderstood, yet super cool device.

The K74 is nothing more then a PC controlled relay board. As far as I know, you must use a parallel port to control the device. There is not a USB option that is available and a USB to Parallel converter will not work. You have to have the hardware mapping from the Parallel port to make this device work.

If anyone has contradictory evidence to this point, please do share a link. I for one would be interested. Moving along…

This post will hopefully cover, the hardware, how to wire it, how to daisy chain, and software to do all the neat stuff you want to do..

DISCLAIMER: DON’T DO ANYTHING DESCRIBED. IF YOU BURN YOUR HOME DOWN OR MURDER SOMEONE, YOU ONLY HAVE YOURSELF TO BLAME.

Numerous sources on the inter-web offer the K74. Some come as a kit, some come fully assembled. When I purchased mine a few years back, I bought the fully assemble version to save time, as time was not on my side. I would expect that the average person with average soldering skills should be able to put this item together in less then an evening. There is very little to it.

Looking at the above picture you see the board. To the left is the Parallel Port (male)connector. On the top row are 8 relays and their respective screw down terminals. The middle row, 8 red L.E.D.’s. These light up when the relay is activated to the “normally open” position. Bottom row, on the left, an I.C. of some kind. Don’t remember its purpose. On the far right 12 Volt DC power connectors, 2 different styles depending on how you plan to power the board.

This board DOES require a 12 volt dc power source. This power is required to activate the relays. These are mechanical relays. As you can see, you have a pin style connector or you can use the screw down terminal. I use the screw down with a 12 volt power supply I purchased from Radio Shack, about forever ago.

When you wire the relay terminal, you have two options. “Normally Open” and “Normally Closed”. Noted as “NO” and “NC”. Looking at the connector, “NC” is on the left, Common “C” is in the middle, and “NO” is on the right. This is where most of the confusion sets in about what to do with what you have. I understand why too, cause the terminology is kind of misleading. But try to follow along.

Common “C” – this is where your voltage, signal, feed, whatever comes into the relay. Be it 110 V, be it 24 V, what ever you are trying to “switch” off or on, it comes in here. Lets say you want to switch on a lamp, the “hot” or black from your electrical wire comes in here.

Normally Closed “NC” – This option allows you to switch “off” an item that is already on, or constantly on. Remember the lamp from above? Lets say you want the lamp to always be ON, the hot wire or black would go in the “C” terminal (as above) then come out the “NC” terminal, on its way to the lamp. The lamp will be ON until you tell the relay board, thru your computer, to do otherwise. Lets say you have a room with a light in it. The light is on, a person comes in and triggers a motion detector, in this case the lamp will turn off, leaving the person in the dark.

Normally Opened “NO” – This is exactly opposite of the above. The “lamp” will turn on when told to do so. So, lets say a person enters the dark room, they trigger a motion detector, the lamp turns ON. There is light.

This may seem confusing, the best thing to do is to wire up one relay and play with it.

Just remember that voltage from the wall or source comes INTO the “C” or middle terminal. NC turns on off, NO turns off on. Simple eh?

Now, we need to decide what we want to do with all these relays. These relays will pass just about any signal or voltage, also the fact that the relays are all independent of each other is quite useful to the home haunter. If you want to run 110 volts thru number 1, 24 volts thru number 2, an audio signal thru number 3, and 1.5 volts thru number 4… you get the idea. And you don’t have to use all the relays at once. Lets play…

The above pictures shows a standard electrical outlet. The screws on the left of the outlet are “silver” and intended for the white neutral wire from the wall. The screws on the right side are “brass” and intended for hot/common black wire from the wall. There is also a green ground screw.

Lets assume that you have an extension cord laying around. Slice of the female end and you will have 3 wires. That is assuming your using a 3 prong grounded extension cord, which I highly recommend.

This simple drawing should pretty much some it up. Just remember, black goes to the common on the relay, then from the relay to the “brass” terminals on the outlet. The white wire goes directly to the “silver” screws on the outlet. The white wire does not connect to the relay in any sense. The relay… is a switch. That’s all. I forgot to draw in the ground wire, PLEASE use a ground. You or some one else could die if this device is not properly grounded. Naturally you would want to put the receptacle in a box of some kind.

“The daisy chain”. Lets assume that you want 110 volts (or whatever signal) to go to more then one relay. Well, you could wire a plug to each relay, but that would be impractical because you would then need 8 receptacles on the wall to plug into. Unless your dealing with high voltages and or high loads, I would just daisy chain the relays.

continued

**FarmerChad** · 12-13-2010,12:29 PM

As show above, you simply connect a piece of wire from one common terminal to another common terminal, in a chain. Making sure to use wire that is suitable for the voltage, a piece approx. 2 inches long, stripped on each end approx. ¼ inch then connected from one common to another. This will carry 110 volts to each relay that is connected… hence the daisy chain. You can do all 8 relays this way if needed. This simply will allow you to use one extension cord, instead of having one for each relay used.

Once you determine if and how many relays to daisy chain, your black wire continues out of the relay on its way to the device to be controlled, in our example, an electrical outlet.

Your daisy chaining efforts will probably look something like this!

The outlets. Now continuing on the assumption of daisy chaining, we want to daisy the outlets in the same fashion. The difference is that the outlets will daisy chain the neutral. Opposite of the relay board.

continued

**FarmerChad** · 12-13-2010,12:34 PM

Here we have some outlets to daisy chain. Only 4 are shown for clarity.

The outlet on the left is outlet number 1, the neutral is coming from the extension cord. To daisy chain the outlets, simply connect a white wire from one “silver” terminal of an outlet, to the silver terminal of the next outlet. You will notice on the outlets that both sides have 2 screws. This is intentional and for the exact purpose of daisy chaining in residential construction. Saves on wire. Just be mindful of where your wire is going.

After you daisy chain the neutral, then connect the black/hot/common wire from the relay to the appropriate “brass” terminal on the outlet. Once again, I did not draw in the ground. It is CRITICAL that you use the ground. When your done daisy chaining and and attaching the black wire you should have something that resembles the below picture.

Your efforts will probably yield something similar. Its imperative that you properly ground these outlets. Other wise you could kill, harm, maim, or other wise set an innocent bystander on fire. We don’t want that.

I hope to update this some more in the near future with other thoughts as to what to do along with the software to make this happen. Any questions? PM me.

**Halstaff** · 12-13-2010,03:26 PM

Great how to! It cleared up all my questions.

**MET42** · 12-13-2010,03:54 PM

FarmerChad
I for one love you explanation on “How To” a K74 board. Thank-you. I used one of these this year for my yard haunt and it worked great. I controlled my talking skulls and Conjuring Madame Leota with it. I just wished I had this thread this year to help make life easier. Anyway, I just wanted to let you know that this board does come with a USB port - (http://store.qkits.com/moreinfo.cfm/KTA-223). I used the Serial port myself but I was thinking of maybe using one of these for the prop - Flickering Pumpkins. If you or anyone else has ideas for uses for this board, please let all of us know.

**FarmerChad** · 12-14-2010,04:50 AM

Originally Posted by MET42

FarmerChad
I for one love you explanation on “How To” a K74 board. Thank-you. I used one of these this year for my yard haunt and it worked great. I controlled my talking skulls and Conjuring Madame Leota with it. I just wished I had this thread this year to help make life easier. Anyway, I just wanted to let you know that this board does come with a USB port - (http://store.qkits.com/moreinfo.cfm/KTA-223). I used the Serial port myself but I was thinking of maybe using one of these for the prop - Flickering Pumpkins. If you or anyone else has ideas for uses for this board, please let all of us know.

Thanks for the link. Certainly an interesting item. Will keep that in mind if I need to expand or if something goes astray to my current hardware. I still like the K74 do to cost and its relative ease of use and flexibility. I did see somewhere on the net about adapting that K74 to use USB... BUT I never saw it in action or anything more then claims that it was possible. We know how that goes.