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There are times when you need a firmer grip on life.

Add a binder clip on the end of a clamp arm gives you a stronger pinch.

An M2 threaded end on the arm allows you to change to a different size clip.

A locking knurled nut holds the clip at the orientation needed.

larryd:
There are times when you need a firmer grip on life.

Add a binder clip on the end of a clamp arm gives you a stronger pinch.

They are known as bulldog clips in the UK.

:o I am in love ;) . . .

Tell me more about "silver soldering" stainless steel... I have some stainless I'd like to solder, and it's being a real pain.

Did you read this one already ?

Project construction example and hints

If you are new to making projects, below is a process you might want to try.

Rather than using a prototyping PCB, we will build the following project on a copper clad PCB ‘mother board’.


After you decide what you want to make, draw a schematic of your design showing ‘all’ the components in your circuit.

There are many free PCB software packages for schematic design and PCB layout.

If your design uses a SMPS (switch mode power supply) always add a ‘Ferrite bead’ to snub switching spikes.

Construct your circuit on a solderless bread board to prove that the circuit works as expected.


Gather all parts and finalize their layout; make sure parts will fit in the project enclosure.

We will use some readymade components to simplify the following construction.


Components:

  • Arduino Pro Mini
  • SMPS (step up DC to DC converter)
  • SMD MOSFET
  • SMD 1206 resistors
  • Ferrite bead
  • SMD to THT “daughter boards”
  • Kynar 30 AWG wire
  • 24 AWG stranded wire for off board connections
  • power switch
  • IR LED
  • power LED
  • machined pin headers for the Pro Mini and SMPS PCBs
  • one 3 AAA battery holder
  • .06” single sided copper clad PCB called the ‘mother board’ (for mounting components)
  • .03” single sided copper clad PCB (for manufacturing pads)
  • enclosure/box
  • heat shrink

Tools:

  • drill press
  • 1/10th inch prototyping PCB (referred herein as the ‘matrix drilling board’ template)
  • metal hole punch OR metal shears
  • ultraviolet glue
  • PCB tinning solution
  • 5-minute epoxy
  • header pins for aligning pads to drilled holes
  • 3 pinch clamps
  • ‘D’ engraving bit (used to chamfer holes)

  1. Make a paper copy of the 1:1 mirrored image of our ‘PCB pad layout’.

  2. Tape the layout to the copper side of our ‘mother board’. Note: components that do not have their pins matching a hole location on our ‘matrix drilling board’ need to have those holes drilled free hand. These holes will be referred to as ‘major holes’.

  3. On the paper image, center punch these ‘major holes’; discard the paper image.

  4. Drill the ‘major holes’.

  5. Align the ‘matrix drilling board’ to holes ‘A’ and ‘B’ as seen below.

  6. Tape the ‘matrix drilling board’ to the ‘mother board’.

  7. Use a blue felt pen to mark all pads that need matrix drilling.
    Note: the drilling template allows for accurate drilling of matrix holes.

  8. Drill all the blue matrix holes.

  9. Use an engraving bit to chamfer all BUT the GND holes.

  10. Submerse the drilled board in tinning solution.

  11. Add machined pin headers to the Pro Mini and SMPS boards.

  12. Fit these boards into the ‘mother board’ holes; solder all GND pins on these boards to copper foil.

  13. Punch multiple pads from the .03” SS PCB material. (Alternatively, use a shear to cut square pads from the same material .)

  14. Align and epoxy these pads over the drilled holes, avoid getting glue inside the drilled holes.
    You can use header pins to align the pads to the holes in the mother board. Remove these pins before the epoxy sets.

  15. Align with header pins and epoxy the SMD daughter cards onto the top surface of the mother board; remove the alignment pins before the epoxy dries.

  16. Using the schematic as a reference, make a wiring map.

  17. Solder 30 AWG Kynar wires as per the wiring map.

  18. NOTE: for the daughter boards, the insulation of the Kynar wire ‘must’ go all the way through the mother board.

  19. For strain relief purposes, add UV glue where off board wires leave the PCB.


Sketch for virtual wall and PDF schematic is attached.

VirualWall.pdf (12.6 KB)

Virual_Wall_Irobot_Roomba.ino (1.23 KB)

The following technique should produce particularly good results when you need to make a ‘Mother Board’ (mounting board) for project cases.

Essentially, we make a collage using straight edged pieces of card stock to cover the outline of the bottom of the case.

After taping, the collage is retrieved and used as a template to aid in cutting and drilling PCB FR4 material.

Just added a GRS BenchMate ‘Mounting Plate’ to the basement electronics work bench.

The mounting plate was covered in a previous post (post #545); thought it might be reasonable to mention it again.

Add a ‘Miter box’ to the wooden tapered bench pin to help in cutting headers.

If you are making several copies of a mother board etc., first make a 'Template Drilling Board', use the template to reproduce holes in the copies.

Further to post #845

Stand-alone Pinch Clamp

A ‘C Clamp’ is an indispensable tool in your lab.

In fact, it seems like you never have enough of them.

A problem with these clamps is they have a relatively large form factor.

The following images show using a ‘Pinch Clamp’ in place of a ‘C clamp’.

It has been seen in previous posts the usefulness of the ‘Pinch Clamp’ held in place with a magnet.

Here, the magnet is replaced with an ‘Acorn Nut Foot’. This glides easily on your drill press table and makes drilling easier; this component assembly will be called a ‘Standalone Pinch Clamp’.

The separation of the two fender washers should be >= to the thickness being clamped; the fulcrum is an M2 screw head and an M2 nut giving a separation of ~0.12 inches.

If needed, the tool can be reduced in size by shortening the 6-32 screw.

I find there is less of a chance the pinch clamp will damage surfaces.

![D.jpg|730x701](upload://n0oc0Hfe9eFF8dkbsUtK6QU7hQT.jpeg

Drilling Template Stick (DTS)

Normally a center punch and drill bit will suffice when holes need to be made in a mother board.

There are times, however, when accurately drilled holes need to be made.


Make a “Drilling Template Stick (DTS)”.

Make DTS boards from .062” FR4 glass epoxy PCB material.

Drill 2 mm holes on a 0.5” grid spacing in the board.

The boards shown below are ~6” by 1.5” and ~6” by 0.5 inch.

Double stick tape 320 grit sandpaper to the surface of your DTS.

Use a tapered round diamond file (from the grit side) to clear each DTS hole.

Tape your PCB paper pad template to your work piece.

Center punch all pads on your PCB paper pad template with a prick punch, remove template; put a Sharpie dot on each prick punch mark.

Center a DTS hole over one of the work piece Sharpie marks.

Use 3 Pinch Clamps to hold the DTS against the work piece.

Position the drill bit over a DTS hole, lower the bit into the hole without the drill power being on, turn on the drill power, drill the hole.

A drill press with a foot activated power switch is a good thing to have ;).

If needed, enlarge the holes after the DTS has been used to drill all the holes in the work piece.


In a nutshell, the DTS board prevents your drill bit from skating around when a hole is being drilled.

This is especially true with diamond core bits when you make pads in copper clad material.

A DTS board made from .062” PCB material, should be adequate for a 2 mm (~5/64”) drill bit.

After adding the double stick tape to the support dowel, reduce stickiness by touching the tape with your palms a few times.

This makes it easier to reposition the dowel as you work.

More Pinch Clamps

You can use magnetic pinch clamps to hold a powered-up PCB.

To prevent traces shorting, the clamp’s compression washers need to be insulated from the PCB surface.

In the past I placed paper over the PCB edge to insulate the washers.

Paper was a bit of a headache, so I added 0.78 mm (.031”) FR4 glass epoxy washers to the clamp.

A CNC machine was used to make the PCB washers; however, a bench sander will work too.

Use epoxy glue between the PCB washer and the fender washer; the center and fulcrum holes are matched to each other.

Assemble the pinch clamp.

We now have a magnetic pinch clamp with insulated compression washers.


You can use 1.75mm (.062”) FR4 material and not use the metal fender washer.

The 1.75mm washers can bend, which may be undesirable.

Use 4" machine screws to make your magnetic pinch clamps adjustable in height.

The heavy wing nut and brass knurled nut can be quickly spun to the desired clamping height.