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Clipboard CW Key

Several months ago I had an idea for building a CW paddle onto my SOTA logging clipboard. The resulting prototype, to my surprise, worked out quite well. Since then I’ve built a couple of different versions and used them on 50 or so activations with only a few minor teething problems.

The basic idea for the key is pretty simple - use narrow conductive fabric tape to make opposed keying pads on the front and back of the clipboard by laying out several parallel strips of tape on each side then connecting alternate strips to appropriate terminals of a 3.5 mm stereo jack. Alternate strips on the front pad are connected to the jack’s tip and ground terminals while strips on the back pad are connected to ring and ground terminals.

Put conductive material on the thumb and forefinger of a lightweight glove, connect the clipboard jack to the rig’s key input with a stereo cable, then key the rig by touching the pads with the conductive glove fingers to bridge the gaps between strips.

So it works electrically like a standard paddle but you operate it sort of like a “touch key” but with no external capacitive or pressure sensing circuitry.

Here are some pics that will hopefully help clarify things.

Back side

Front Side

Set Up for Operation

Pros: Minimal weight and cost. Rugged and easy to build. Quite reliable with no moving parts, no extra circuitry, no extra power requirements. A very low profile and no need for special protection when carrying. Works fine with all my SOTA rigs – KX1, KX3, ATS3 and MTR5B – and with the Winkeyer USB at my home station. I don’t see why anything that works with mechanical paddles would have a problem. No need for special mounting arrangements. I just hold the clipboard as I normally do. As far as feel – what feels better than your own fingers.

Cons: Wearing a lightweight glove. To my surprise this hasn’t bothered me and I really thought it would. I’ve been using an old liner glove that lost it’s mate. It’s light enough that it doesn’t get in the way and I’ve been able to send fine at my normal 25 wpm. Experiments with bumping up to 28 or 30 wpm have resulted in normal error rates at those higher speeds.

Here’s a link to a short YouTube video of me sending at 28 wpm on an MTR5B using the clipboard/key.

The clipboard for the key shown is a piece of scrap corrugated polycarbonate sheeting typically used for glazing greenhouses. Interesting stuff - very strong and light. The clipboard/key weight, not counting glove or cable, is right at an ounce. The glove adds half an ounce. To the right in the video are a pair of conductive “finger cots” I made from the cut off liner glove fingers. The cots weigh almost nothing.

A trick that helped me simplify tape layout was to realize you can overlay tape runs without creating a connection by using an intermediate layer of ordinary electrical tape.

A 65 ft role of the 5mm conductive fabric tape I used is available at Amazon for $6.99. The entire clipboard setup certainly takes less than 3’ of tape so there’s plenty in one role to absorb mistakes and/or experiment with other configurations. The tape is reliably conductive on the the adhesive and non-adhesive sides - a must for this application.

Here’s the tape link:
https://www.amazon.com/Conductive-Fabric-Adhesive-Laptop-Shielding/dp/B01ALDR0D0/ref=pd_ybh_a_2?_encoding=UTF8

You can’t solder to this tape. Connections between the tape and hookup wire leading to the jack terminals were made by stripping 3/4 inch of wire and sandwiching the spread wire between two strips of tape. The tape adhesive is quite strong and this arrangement produced good electrical and mechanical connections.

This type of tape is widely used for computer EMI protection or making “paper circuits”. There are many other options on Amazon and I’m sure you can find similar stuff on Ebay, etc.

73,

Mike - ke5akl

13 Likes

Mike,

This is AWESOME!

How does moisture affect it? Have you tried it in the wet?

Thanks for sharing - love it!!

-Josh

A-W-E-S-O-M-E!!!

TU Mike,
Very clever design and the use of ultralight corrugated plastic clipboard.
My approach is heavier and not practical, key must be mounted on note pad.
I use a conductive glove and an IDE connector to mimic your work.
73 and all the best for 2020

Pascal

Very cool Mike!!!

Incredibly clever approach.

For winter activations, I almost always need to wear gloves, usually heavier ones. This style of paddles would seem to work well in that situation

Have you tried this with gloves designed to work on touch screens? I’m wondering if the material used at the tips of those gloves would work without adding the conductive tape.

73 Paula k9ir

1 Like

Pretty clever Mike! I’m off to the workbench now!

73 gary k3tcu

First - thanks to all for the attaboys!

Josh, Given NM’s climate I just don’t activate when it’s rainy - wait a day or two and it’ll be sunny - so I can’t say how moisture would affect the keying surface. I’d guess there’s nylon involved in the conductive fabric so it’s probably hydrophilic. But is that good or bad?

However it’s also possible to make these using copper foil tape. I’ve made one and it works fine. It’s clear that the foil is more delicate than the conductive fabric so I’m not sure how well it will hold up over many activations in the rugged SOTA environment.

A feature of the copper foil is that you can easily solder to it. It’s so thin that the you can produce a good joint with just a touch of the iron. The technique I’ve used is to tin a spot on the tape, tin the wire you’re attaching, then touch the wire to the tape tinned spot. With just a touch of the iron a good joint is made.

Here’s a link to copper foil tape I’ve used that’s reliably conductive on both sides.

73,

Mike - ke5akl

Paula,

The key works pretty well with heavier gloves. I’ve tried a number of times in the field and found I was able to send better than using the same gloves with my paddlette mini-paddle. In fact, with the clipboard key the problem switched from sending to being able to write on my log sheet decently with the thick gloves.

As far as touch screen gloves - I don’t have any so can’t say. However, I just went down with a DMM to a place that sells them and measured the resistance on the touch screen pads across the distance needed to span the gaps on the key. Turned out to be in the range of a 100 ohms. Is that low enough? Don’t know. The corresponding resistance for the conductive fabric tape is less than my cheapy DMM can measure.

73,

Mike - ke5akl

I like the idea, Mike.

73
Peter

hi, clip only

2 Likes

My glove is about 3 Ohm at the touch pad, those pads are not electrically connected.

Grid mesh and finger tips has only 1.8 pF stray capacitance.

Cheers, Pascal.

If I did that you wouldn’t see another spot from me until mid-July! :rofl:

Thanks for sharing this idea. I’m going to experiment…

-Josh

1 Like

Josh,

Climate is one of the best things about New Mexico. There are 4 seasons but nothing is too extreme.

As far as experimenting - here’s some stuff I learned by trial and error.

For the best electrical tape-to-tape connection sandwich between 2 pieces of tape. For instance, if you look at the pictures of the pads above you’ll see there are vertical rails on the left and right sides with horizontal strips alternating between rails. To build this I laid down the rails, then ran the horizontal strips with as much overlap with their rails as possible, then laid down second pieces of rail tape sandwiching the horizontal connection areas. That has given a good, long-lasting electrical connection.

You can make a turn in continuous fabric tape by folding it back at an angle, exposing the adhesive side, then doubling back in the direction you’re aiming at. This is most useful when running tape to the connector hookup area. This technique doesn’t work as well with the delicate copper foil tape.

For the best electrical and mechanical connection when connecting hookup wire to conductive fabric tape, strip about 3/4 inch of wire, then sandwich the wire between two layers of tape with the bare wire strands spread as much as possible. Press the tape on very firmly and work the tape between wire strands where possible. It can help to make a wider connection area using a few overlapping tape strips to give more area for spreading the strands. I’ve had no mechanical or electrical problems connecting wire to tape this way.

If you’re using copper foil tape you can just solder the hookup wire to the foil. Turns out this is quite easy to do as I described above. In fact you can also solder the copper foil tape-to-tape junctions easily. Just hold solder onto the junction line, touch the area with the iron and it will flow quickly onto both sides.

Seems you could make a hybrid joint but laying down a strip or copper foil tape, soldering the wire to the copper tape, then overlaying the copper foil strip with a conductive fabric strip. I haven’t found this to be necessary so haven’t tried it.

If you have any problems feel free to let me know here or to email at the address on my QRZ page and I’ll do whatever I can to help.

73,

Mike - ke5akl

All very ingenious I’ve got to say. I always prefer use a tiny (2" or 3") ex eastern European military key andmy only bugbear is gloves V. frozen hands in cold weather.

So I might just try to make myself something like you’ve posted. Thanks.

Some folks asked about use with heavier gloves so I made a video sending with 3 thicknesses of glove ranging from a thin liner glove to a heavy and very warm ski/snowshoeing glove.

The medium weight glove used has touch screen pads on the thumb and forefinger. I show that the pads work fine with my smart phone but are not conductive enough to work with the key. Apparently the pads on these type of gloves vary widely in conductivity. – Note: Thanks to Pascal for taking the time to measure the conductivity of his gloves.

Here’s a link to the video:

In the video I use a new key made a few days ago using copper foil tape. The key works fine here at home but hasn’t been tried it in the field yet. The copper foil tape is delicate compared to the conductive fabric tape I’ve used on previous keys and I’m not sure it will hold up to the rigors of SOTA use. We’ll see.

Thanks and 73,

Mike - ke5akl

2 Likes

Just a quick comment - since my last post I’ve used the copper foil key a number of times in the field. It’s worked flawlessly and seems to be a holding up well.

73,

Mike - ke5akl

1 Like