In the next pages the capacitor arrays will be assembled and mounted on two birch plywood panels (each 9” x 15”). Since 2 panels have 4 sides, 3 of the sides are reserved for capacitors. I used “cable tie mount bases” (Home Depot) to secure the capacitors to the panels. For single capacitors I used the adhesive back to secure the mount base but where larger capacitors were involved, I used #6 x 3/8” Phillips screws to secure the mounting bases to the panels. An easier way to mount the capacitors is to drill holes through the panel and use cable ties. If you use a metal mounting panel you will need to use rubber sheeting to keep the metal capacitors from contacting the metal. Gene Dillman found considerable stray current in his metal cabinet but solved the problem by insulating the metal capacitors.
These are two of the cable tie mounting bases. They have slots for the cable ties to pass through and up around the capacitors. The ties are 7 inch ties and are just long enough for all the capacitors used in a DCM. The mount bases have an adhesive backing but when mounting the larger capacitors there is some prying action when you tighten the cable tie and the adhesive releases. This prying occurs because two bases are used for the large capacitors so they can cradle in the gap between the two mounts.
This is the 30 µf capacitor. The dark strip of wood on the left edge of the panel is a cap of cherry that hides the edge of the plywood when this plywood was used as a shelf long ago.
This 30 µf (PART 225-5010) capacitor is the only one on switch B. I label all capacitors to avoid mistakes in wiring to the switches. Avoid pulling too tightly on the cable ties. The capacitors shouldn’t move around but make the tie just snug enough.
These capacitors for switch C, each 8 µf (PART 591-7045) will be connected together in a parallel circuit so they should be mounted near each other.
On the next page these capacitors will be connected in a parallel circuit
The 4 µf (PART 591-7025) capacitor for switch E has been mounted to the panel and above the 8 µf (PART 591-7045) for switch D will follow.
The short pieces of 12 gauge wire have their ends stripped of insulation and the spade connectors will be crimped on. These wires are used to connect the two capacitors in cap array C together in a parallel circuit.
Use this section of the crimping tool to secure the connector to the wire – be sure there is no wire insulation in the aluminum collar that will be crimped. Also be sure that the wire does not turn independently of the connector –if it does crimp It some more. Notice how flattened the yellow insulation is where the crimping pliers were used
The capacitors used in a DCM do not have plus and minus terminals. By connecting the top terminals together and the bottom terminals together you get a parallel circuit (even if you turned one of the capacitors 180 degrees and rewired it. Here the panel is lying flat and in the picture to the right it is upright on its edge – the way it will be mounted in the cart.
Here is the entire side of the first panel. There is no capacitor for switch A. Switch A is used for frequencies that require capacitances larger than 62µf which is the sum of all capacitors in a DCM.
These 4 µf (PART 591-4205) capacitors for switch F will be in a series circuit. It doesn’t matter which ends you twist together. Hold them as shown. Leave about !” of wire Is between the capacitor and where they cross. They will be twisted together with fingers so once you start the twist be sure to pinch the spot where the wires cross so the twisting doesn’t migrate down toward the capacitors.
They don’t all work out to be this neat but this one makes a good picture.
Trim the ends but not so much that the twist is loose. All of the twist connections like this must be soldered
Decide where you want to place them then attach mounting bases and cable ties or drill holes and use cable ties.
This series connection of 2 - 4µf (PART 591-4205) capacitor will be connected to switch F
For switch G three 3 µf (PART 591-4200) capacitors will be connected in a series circuit
Twist the wires together as before - place the array to determine the location of mounting bases. Using a marker to label helps when wiring the capacitors together. Its just another way to keep yourself organized
series
parallel
Capacitor array H two 1 µf (PART 591-6085) to be connected in series to switch H is shown mounted on the panel. Notice that the wire twists that will be soldered are all out where a soldering iron can be used very easily.
The capacitors for switch I involve a parallel and a series circuit. First connect two .47 µf (PART 591-6075) capacitors end to end. Use needle nose pliers to make a bend In each of the free wires so they are perpendicular to the two joined capacitors. Connect a .015 µf (PART 591-6150) to these free wires which results in a parallel connection I used pliers to twist these connections since the available wire for the parallel connection is limited in length.
Just a few more arrays on this panel will be enough.
Switch J is connected to capacitors in a parallel circuit. Connect a .1 µf capacitor (PART 591-6175) front to front and back to back to a .022 µf capacitor (PART 591-6155). They are shown here mounted to the panel.
F
H I
G
J
Switch K is connected to two capacitors connected in a parallel circuit. Connect a .047 µf (PART 591-6165) capacitor front to front and back to back with a .015 µf (PART 591-6150) capacitor. Don’t twist the wire so much that the capacitors get close together.
K
The second panel is finished. All the wires on the left of each array will be connected to their respective toggle switches. The wires on the right of each array and all other capacitor arrays will be joined together and go to one of the terminals on the binding post. The binding post is where the coil plugs into the system with banana plugs.
We are now working on the second panel (the third side for capacitors). This side will contain the remaining capacitors and the other side of the panel will contain the resistors. Shown is the capacitor for switch L. It is a single .033 µf (PART 591-6160) capacitor.
This is another single capacitor for switch M. It is a .015 µf (PART 591-6150) capacitor.
Switch N connects to this Single .01 µf (PART (591-6145) capacitor.
Switch P connects to this series of two .01 µf (PART 591-6145) capacitors.
Switch O connects to this series circuit consisting of two .015 µf (591-6150) capacitors. The switches are located to the right. Both panels will be mounted in a perpendicular direction to the back of the switch panel
Soldering capacitor arrays Soldering is easy and fun. Be very careful with the hot soldering iron tip since it would be very easy to melt a hole in the casing of a capacitor. Ventilation is a good idea because the flux in the hollow core of the solder wire vaporizes when you melt the solder. Vaporized flux damages the eyes and lungs. Once the soldering tip is hot, touch the wires to be soldered and melt some solder on the tip of the soldering iron. The solder flows by capillary action so to ensure that it seals the connection, heat just long enough until you see the solder appear to sink into the joint.
The soldering iron tip is under the twisted wire to be soldered. The idea is to get the solder melted and onto the twisted wire quickly. Heating too long can ruin components like capacitors.
This is a strip of solder coming directly from a 1 lb. spool.
Connecting the capacitor arrays to the switches Each capacitor array has been lettered. It would be wise to check each array (before soldering) to be sure that where a series circuit is needed you actually do have a series connection and not a parallel connection. I chose to use solid 12 gauge wire to connect the capacitor arrays to the switches because there is always enough left over from coil winding but you could use stranded wire instead. Stranded wire is much easier to use than solid wire since it bends so easily.
A wire is soldered to one end of each capacitor array and then goes to the bottom spade terminal of the respective switch. In the case of the large metal jacketed capacitors with spade terminals, a spade connector is crimped to each end of the wire so no soldering is necessary. The switches shown have 3 male spade connectors. Switches with just 2 are easier to use since you don’t have to figure which one is not used.
Here a spade connector is pushed onto one of the two terminals of the 30 µf capacitor for switch B. Each of the 2 terminals has 4 spade connecting spots. You can choose any of the spade ends but when we connect all the capacitors together later you must use the other terminal to connect a wire to. The grey wire shown goes to switch B so the upper terminal with 4 spade ends is the one we must use later. After all of the capacitor arrays are connected to switches the wire on the other side of each capacitor array are all connected together and will go to the binding post where the coil plugs in.
The 30 µf capacitor is connected to the bottom spade end of switch B.
You can choose any of the 4 terminals on these parallel capacitors to connect to the switch. I chose the one on the lower capacitor and the terminal back toward the panel. The grey wire is going to switch C. When we connect all the capacitors together later, the terminal away from the panel (on either capacitor must be used).
This wire from capacitor array C is connected to switch C.
Connecting capacitor arrays that don’t have spade terminals requires soldering directly to the capacitor wire. An easy way to do this is to use about 3” of a strand of stranded wire and wrap the copper wire going to the switch and the capacitor wire together. Its easy to solder the connection this way. Another way to make this connection is to wrap the capacitor wire around the thicker 12 gauge solid wire and then solder the connection
Capacitor array F is connected to switch F. You can connect all the other capacitor arrays to their respective switches but I recommend that you first do the operations on the next few pages. The reason is that finishing the capacitor to switch part is easy – just push the spade connectors onto the lowest terminal of each switch. The next steps require a lot of finger room and will prove to be easier if all the switch wires were not in the way.
To avoid photographs that were mostly masses of wires and clumsy to work around. I do not have the switches and capacitor arrays connected to their switches in the next several pages. The next step is to cut 31 four inch long pieces of stranded 12 gauge wire. Strip 3/8” of the insulation off one end of 16 of the pieces and crimp a spade connector to that end. Strip about 5/8” of the insulation from the other end of the 16 wires. Attach the spade connectors to the middle terminal on the back of each switch. Spread the strands into a fan to make the next step easier. The top-most terminal on each switch is not used. There is an alternative method for this wiring shown in the last section of this tutorial.
Take the remaining 4” sections of stranded wire and strip 5/8” on insulation off of both ends. Spread the strands into fans as shown above.
Take 2 of the wires you just stripped and fanned and place them with the 4” piece of fanned wire connected to switch H (top left on the back of the switch panel). You will be twisting three pieces of wire together with your fingers. The fan shape make twisting easier.
Here two of the pieces of wire and the wire attached to switch H are twisted together. Don’t use pliers to twist since many of the fine strands may be broken. It is sufficient to use your fingers. Use an alligator clip or two to hold the three wires in place for soldering.
The connection has been soldered. When the solder cools use a red wire nut to cap the connection. The stranded wire that is almost vertical in this picture will be twisted with the wire immediately behind it and another loose piece of wire. What we are doing here is using the loose pieces of wire to “jump” from one switch to the next. In the end all switches will be connected together. The piece of wire pointing to the left coming from the soldered connection will be twisted with the wire below it and a loose piece of wire.
Keep connecting the set of wires until you get to switch A. There are just two wires to twist and solder for this switch. All of the twisted connections should be soldered and capped with wire nuts.
This photo shows the detail of switch H. Notice that the wire nut has two “jumpers” which allow you to continue across the top row of switches to the right to switch A and down to the bottom row of switches to the right to switch I. When you get to switch I do not solder until you see the next page.
When you get to switch I add in about 9” of stranded wire (I used black so you can see it in the picture. This black wire will be connected to both set of resistors
switch I
Notice the grey wires that are soldered to the bare copper wire that connects a set of resistors. The grey wires go to the left and are attached to the black wire. The black wire goes behind the wood panel to the wire nut that leads to switch I as shown in the picture to the left. The above resistor panel is not in the picture to the left – it was added to show how the resistors connect to the switches. Building the resistors sets is discussed in the resistors section.
The grey wires coming from the left side of both resistor sets go to the black wire and then to the wire nut at switch I.
The other two grey wires go to the right and go the back of the amplifier. Notice they are soldered onto the bare copper wires connecting the right sides of the resistor sets.
Connecting all of the capacitor arrays
Notice how grey wires go from a terminal on a capacitor to the switches. Also notice that grey wires now attached to the other terminal go back toward the left. The wires will be connected together and with “jumpers” will be connected to all of the other capacitors.
Here are the rest of the capacitors on this panel showing the grey wires going to the left. The top two capacitors labeled C are actually identical in size. The photo was taken at an angle which suggests that the top capacitor is larger. Notice that the wire going to switch C is connected to a different terminal than the wire going to the left. Both of these wires could have been attached respectively to the other C capacitor at the top.
A large blue wire nut secures all of the capacitor wires. Notice that a “jumper” wire goes to the left and through a hole to connect the other capacitors on the other panels. An extra wire is joined to the blue wire nut and goes to the binding post where it will be soldered. The wire insulation on the end of this wire is stripped so the bare end can be wrapped with a strand of copper wire and secured to the post for soldering.
Grey wires were soldered to the ends of the capacitor arrays and twisted with electrician’s pliers and will be soldered. The wire to the lower left is a “jumper” that will connect with a group of capacitors mounted on the panel to the right. Again notice that the wire on the other side of the capacitors will be connected to their respective switches but are not yet connected in this picture This picture shows the 3rd panel of capacitor arrays – the other side of this panel is where the resistors are attached.
There are too many capacitor arrays on these two panels to twist all the wires together so I made three bundles of wires connected by “jumper” wires. The arrow points to the “jumper” that is already connected with the wire nut to all the capacitor arrays on the panel to the left. The next page shows the 3 bundles.
•
The
There are 3 jumper” wires in this picture. The wire bundles with grey wire nuts were composed of fewer wires so required a smaller wire nut. See an alternative way of connecting the capacitors together at the end of the tutorial on the “New and Alternate Ideas Section. The unseen side of this panel has all of the metal jacketed capacitors on it. The blue wire nut connects all of those capacitors together.
This is the wire nut connecting all the metal jacketed capacitors – the “jumper” wire connects this panel of capacitors to all the other capacitors.
Resistors There are 10 resistors in a DCM. They are connected in two groups of five resistors each. The wires coming out of a resistor are not quite long enough to twist all five resistors together and still have space for cooling around each one so I mounted each one on a cable tie mounting base.
After 5 resistors are mounted and strapped down, strip a length of solid 12 gauge wire of insulation and wrap about !’ of each resistor wire around the solid copper wire. Do the same thing on the other side of the resistors. Each resistor could easily be held in place by drilling holes and using just cable ties.
The resistors on the left have been connected to each other on both sides. Mount the remaining 5 resistors on mounting bases and connect them together also.
Here are the 2 sets of resistors. The resistor wirecopper wire connections should now be soldered.
Choose the side of the resistor sets that is closest to the back of your QSC1850HD amplifier. Two solid copper wires must be connected to teach resistor set and one must go to the Channel 1 Minus output terminal and one must go to the Channel 2 minus output terminal on the back of the amplifier. Since my DCM is completely contained on a cart, I had to drill a hole in the shelf that holds the capacitor arrays and resistors to allow these wires to pass down to the first and lowest shelf to the amplifier. The two copper wires are hard to hold in place while soldering since you will have a roll of solder in one hand and the soldering iron in the other. Use one thin strand of wire to wrap the two together and then solder the joint and all the copper wire-resistor joints.
It doesn’t matter which set of resistors is connected to the amplifier Channel 1 minus output terminal. Connect the other set of resistors to the Channel 2 minus output terminal. Here are two copper wires that lead to the amplifier channel 1 an 2 minus output terminals. The wiring for the other side of the resistors is discussed in the section on Capacitors.
One set of resistors should be connected to Channel 1 output. The other set of resistors should be connected to Channel 2 output.
Wave/Signal Generator Many people wonder how a DCM can pulse a magnetic field at a given frequency. It’s easy – you choose! A DCM has as an integral part, a wave generator but you must purchase a wave generator that produces low frequencies. – in the Hz range (for waves such as 306 Hz, 432 Hz, 625 Hz, 2112 Hz). A short online survey of wave generators will quickly show you that most produce waves in the mega Hertz (MHz) millions of waves/second and many produce Giga Hertz (billions of waves/second) frequencies. A wave generator such as these will not be compatible with a DCM. You must have a wave (sometimes called a signal or audio) generator that emits very low frequency waves - as low as you can go toward zero waves per second. The Instek SFG-2004 generator produces waves down to .1 Hz (waves per second).
This is a BNC jack – the cable supplied with the generator has a BNC connector on one end And alligator clips on the red and black wires that split from the main cable. You can change the clips to fork connectors that fit under the screws on the back of the amplifier if you choose
This is the Instek SFG 2004 signal Generator..
Coil Stand •
I designed a coil stand that holds the coil off the back of the stand about ! inches for better cooling. There are four short 1 "” long dowel pieces glued in #” deep holes. Each of these pieces has a "” hole drilled through it so the coil can be strapped down to these support pillars with 4 cable ties. The weight of the coil is further supported on 3 dowels that are 3 #” long and glued into #” deep holes (so 3” of each dowel sticks out of the back of the stand. This dowel length will accommodate coils that are as wide as 2 #”, which is wider than the vast majority of coils used in coil machines. The coil shown is an 8.51 mh coil. The stand is made of red oak. The base is 1 1/8” thick and the tilted back is 7/8” thick. The angle between the back and the base is 14 degrees.
Cutout for handle allows coil to be moved but not abraded by constant handling. Cutout was made by drilling overlapping 1” holes with a Forstner bit with a drill press.
The cable tie goes through the pillar and around the coil – there are 4 pillars holding the coil off the back
The coil rests on three 1 inch diameter dowels in addition to being strapped to 4 pillar supports with 4 cable ties. The two bottom dowels are really the only ones needed for support.
Top support pillar
Bottom support pillars
The top right shows that two pieces of red oak have been glued together to make a wider piece for a coil stand base. The dried glue is shown along the glue joint. I use polyurethane glue exclusively. The wood must be slightly dampened to activate the glue but when it cures in a day its very strong.
The slanted blades shown (an adjustable dado cutter) consists of two blades that rotate around a wedge that tilts one blade so grooves (dadoes) of various widths can be – up to 7/8”. The saw is tilted 14 degrees to give the tilted dado. This helps to move the center of gravity of the 9 lb. coil backwards and stabilizes the stand
A spindle sander is great for cleaning up the insides of cutouts. I drilled 1” diameter overlapping holes to make the cutout. This is the vertical part that holds the coil. Here it is being planed so it fits into the slanted dado groove
The 3” radius curves have been cut of a bandsaw for the edges. The piece on the right is the base and the piece on the left is the upright
I could do without the sanding part but there are parts for 3 coil stands here and they all need a lot of sanding.
The 4 one inch circles will be drilled 1/2” deep with a 1” diameter Forstner bit. One inch diameter and 1” long dowel pillars will be glued in these holes for the wire coil to sit on.
The 4 dowel pillars have a 1/4” hole drilled so a cable tie can be put through the hole and around the wire coil. This straps the wire coil to the coil stand. Be sure to drill the hole before the pillar is glued in its hole and be sure to turn the pillar in such a way that the cable tie will go through the hole and around the wire coil without twisting.
The other 3 one inch holes are for longer dowels to support The weight of the wire coil. The coil for this stand is 1 !” thick and the holes are 3/8” deep so the dowel supports end up about 2 3/8” long (they are slightly longer than the coil is thick).
All dowels are glued in place.
The wire coil is strapped to the 4 short pillars with cable ties and the wire coil sits on the 3 longer dowels. A more universal stand would be to eliminate the long uppermost dowel. Coils of different sizes could then just sit on the two lower large dowels.
Three glued stands. They will dry overnight. The cured glue usually squeezes out and must scraped off with a sharp wood chisel. I use one coat of a tung Oil..
After removing any glue (with a narrow, sharp chisel) that squeezes out around the dowels, the stand is sanded and coated with tung oi lfinish. I let it dry for a day and then mount the coil with cable ties that pass through the short dowels and around the coil.
Here the cable tie has been pulled tight and the end has been trimmed.
This is one of the 15’ long speaker wires that will attach to the coil on one end and to a banana plug on the other end. It has been stripped of its Insulation (about 1/2”) and twisted around one of the solid copper wires of the coil. An alligator clip is very handy for holding the two wires while they are soldered.
The connection has been soldered. Cut off any of the stranded wires that stick out and trim the length of the solid wire if it sticks out. Use a wire nut to insulate the connection.
This is a finished coil stand with an 8.51 mh inductance coil. The coil’s dimensions are 2” wide and 1 ! inches thick. This section on building a coil stand is not intended to show the best way to support a coil. The intent is to generate ideas when one way of supporting a coil is shown. This design however is especially nice to hold in your lap while sitting.
Connecting the speaker wire to the banana plugs
Unscrew the plastic insulator from the plug. A small adapter (not shown) was screwed into this plug in case the user wanted to solder very thin wire Into the plug – just discard this part. These plugs were purchased from http://www.elexp.com but many suppliers have Them.
I used regular pliers to hold the banana plug. To hold the pliers in a closed position without squashing the tip portion of the banana plug, I used masking tape on the handles. Strip about 3/8” of the clear insulation off the ends of both wires and be sure to put the red and black insulators onto the wires before soldering.
Hold the flat bladed tip of the soldering iron against the threaded end of the banana plug. It will be hot enough to melt solder in about 30 seconds. Put the end of the solder into the hollow end of the plug and almost fill it with molten solder. Put the soldering iron down and quickly pick up the end of the speaker wire and insert the well twisted stranded wire end into the molten solder. Hold it there for a few seconds until it is secure. If you fill the end of the plug with too much molten solder, it will run out and into the threads of the plug. You might have to file the threads off if the solder is too thick. Taper the end of the plug with a fine file so the plastic insulator can be twisted on without stripping the threads inside. It’s a lot easier to not fill the hole with too much solder.
The color of the insulated plastic barrel has nothing to do with the color of the wire in the above picture. The other end of the speaker wires will be connected to the two wires on the coil – do it wrong and there will be a huge explosion – just kidding – just connect them.
Doug Coil Machine on a Cart I designed a cart for my DCM so all components could be in one place and also be portable. Since the QSC1850HD amplifier is the largest part and heaviest (50 lbs.), the cart’s dimensions are based on it alone. The lowest shelf holds the amplifier, the second shelf contains all of the capacitors, resistors, and wiring to the switches. The top shelf holds the coil stand, the multimeter, the signal generator, a stop watch, and a printout of the frequencies and switches. The next pages will show the cart but not all the woodworking details. The legs and shelf supports (stretchers because they hold the legs in place) are all made of red oak. The shelves are !” oak-veneered plywood. The wheels are 2 "” diameter rubber swivel wheels (Home Depot). I am presently designing a model that will eliminate the cart. The electronics will be in a frame and panel red oak cabinet that will fit exactly on top of the amplifier and will itself be about 7 or so inches high.
The 16 switches are here
The binding post is here
The bundle of wires goes through a hole in the top shelf to the signal generator and the multimeter The 2 white wires go to a signal generator + and – output terminals, they come through the hole leading down to the amplifier
The side panels have cutout hand-holds. I The cart seemed like a great idea because it is mobile but it turned out to be in the way most of the time. The last section of this tutorial has some details of an oak cabinet that has the same footprint as the amplifier.
The two sets of resistors are here One of the black wires is the power cord for the signal generator on the top shelf. The other black wire and the red wire are the test leads from the multimeter located on the top shelf. The red and black alligator clips are shown attached to a set of resistors.
This is the cart with the top shelf removed so you can see the electronics shelf. This is the first DCM I built and is not the one photographed for this tutorial but is virtually identical. You can easily see the three panels of capacitors. If you go through the tutorial a few times you will recognize everything that is here.
Each vertical plywood panel is held upright by twos !” x !” X 19” wood strip on each side of the bottom of the panel. They are just screwed to the shelf. An additional screw or two could be placed horizontally to the shelf through the wood strips and into the panels. The vertical panels are not attached to anything at their tops
New and Alternate Ideas Section 1. The twisting of capacitor wires together with wire nuts is messy looking. It certainly works but here is an idea for a neater look. Radio Shack (and many others) sells terminal blocks. You will need 3 if you have 2 upright panels containing capacitors and resistors but just 2 if you have all of your capacitors on one surface (shelf). The screws across from each other on a terminal block are connected electrically but not to any of the other screws. Here is a way to make all the screws have continuity. The jaws of wire stripping pliers have grooves on the jaws that grip very well. Strip about 2” of the insulation from some 12 gauge wire. Use the pliers to grip the wire about 1/8” from its end. Turn the pliers to bend the wire into a small loop. When you have a 180 degree bend use the pliers to squeeze the bend into a tight U-shape. Make sure the ends of the U are just far enough apart to fit between 2 adjacent screws on the terminal block. You may have to adjust the shape of the U with the pliers. If your terminal block has 8 sets of screws you will need 7 U-shaped bends of wire. The pictures on the next page illustrate this idea.
This is a terminal block. Each set of 2 screws between the black dividers are connected together with a metal plate beneath the screws. To get all the screws connected together you need to use jumpers or bridges.
Here a loop of wire was formed with the stripping pliers and then the loop of wire was squeezed into U-shape.
Every screw on the top row can have 2 wires attached to it (on its left and right sides). Notice the two end screws on the bottom row – 1 more wire can be attached on each side of the terminal block for a total of 18 wires. The black plastic is a good insulator so the block can be screwed down to a mounting surface.
The 4 wire nuts in this picture connect the wires from 15 capacitor arrays and 3 jumper wires to connect the capacitor arrays together - it makes for a busy look. Three terminal blocks (one for each capacitor panel) would be mounted on the panels and each of the wires going to the wire nuts would instead go to the terminal blocks. Only 2 jumper wires would still be required to get from panel to panel. If all capacitors and resistors were mounted on one flat surface – only 1 terminal block would be needed. The 8 screws could each accommodate 2 wires from capacitor arrays plus the ends of the block containing the copper loops has 2 spots for 2 additional wires. There are actually 18 places wires can attach.
2. Most people do not have complete wood shops for cabinet making. Here is an idea for a simple structure but not in (because the electronics are exposed) a household with children or pets unless you could restrict access to the coil machine when it is in use. To look balanced, the base of this structure should be same size (or less) as the length and width of the QSC 1850HD amplifier since it would sit on top of the amplifier. Short feet, chair feet protector buttons, or small blocks of wood could be attached to the base to allow for air circulation above the amplifier.
The !” thick panel should not be thicker because the switches would not be long enough to secure the threaded collar to tighten them onto the panel.
A few screws will hold the panel to the base.
switches and binding post go here capacitors and resistors This base sits on the amplifier
3. Another idea is to eliminate the extra wiring with jumpers and wire nuts to connect the switches together. A simple solution would be to use #30-305 switches (the switches used in the tutorial #30-310 could be used as well) which have 2 terminals and on/off switch action. On pages 82-85 a wiring method is shown to connect all the switches to each other with the red stranded wire. All of this could be eliminated by mounting one terminal block on the back of the switch panel (and use copper U-shaped jumpers to connect all the screws on the 2 row, 16 screw terminal block together) . Use a length of solid 12 gauge wire with a spade connector on its end to connect to the bottom terminal of the switch. The other end of this wire would be connected under one side of a screw of the terminal block. Do this operation with every switch so that 16 switch wires would go to the terminal block. Two additional wires would have to come out of the terminal block and go to the two resistor sets to connect them into the system.
A much more compact DCM than a cart model is the frame and panel cabinet model. The cabinet sits on top of the amplifier so the footprint is as small as possible. The main disadvantage is that the space inside the cabinet for capacitors and wiring is much more limited so the capacitor and resistor layout is more important since space cannot be wasted. I decided to place the resistors on a small vertical panel.
vertical resistor panel
terminal blocks instead of twisting wires and wire nuts
This is the back of the switch panel (switches are #30-310 – see the Word document “Coil Machine Parts List” on the CD for the source for the switches - with 3 spade terminals). If you would mount a terminal block above the switches you could simply attach a wire to a switch’s middle spade terminal and attach the other end of the wire to the terminal block. To do this with all switches would connect all of them electrically. Switch #30-305 only has 2 terminals so you would connect the wire from the correct capacitor array to the bottom spade terminal. The wire going to the terminal block would attach to the switch’s other terminal. A terminal block in this situation would save a lot time (no twisting of wires and no soldering). Since the switch panel is 1/4” plywood you cannot attach the terminal block with screws. One way around this problem is to glue a strip of wood about the width of a terminal block but about 1/2” longer onto the panel. You will need to clamp the wood strip and let the glue dry overnight. Place the terminal block on the wood strip – mark where the holes are located and drill small holes in the wood strip and attach the terminal block.
I would be very pleased if anyone who invents an improvement in design or finds an easier way to do any of the things shown in this tutorial would email the ideas to me. Especially important would be structures to house the electronics portion of the Doug Coil Machine, coil stands, wiring improvements and I will incorporate them into this tutorial either in the main body or in this section. The idea is to make the construction of this coil machine as clear and as uncomplicated as possible for anyone to build. Your name will be attached to your ideas.
Encouragement Page That’s all there is. I hope everyone who views this tutorial will do it more than once because it will become more and more clear as you begin to understand initial points. Don’t give up and say I can’t do it because you can start and finish a Doug Coil Machine. Just think for a second that this might be the best accomplishment, as far as making something is concerned, in your entire life. I cannot believe that anyone who built a Doug Coil Machine would feel bad about it afterward – you will not only feel good, but the most important point is that you will be helping yourself. If you have questions, I would be most happy to hear what you need to know. Thanks for your interest, John Stolar
[email protected]
