Topics

Ultra light pressure sensor based paddle

VK3IL
 

All,

I've been experimenting with a new design for a no-moving-part CW paddle for SOTA that is based on pressure sensors rather than capacitive style. It was inspired by a similar design described in QST in Feb this year, but redesigned to require no battery and be as compact as possible. It weighs just 26g (including the cable), so will hopefully make a useful addition to the SOTA kit.

I thought it may be of interest as a complement to Steve's rigs. I've tested it with both the MTR2 and the Soda Pop and seems to work fine, but note the comments in the blog article of potentially needing a slightly stronger pull-up on the key lines.

I've written up the details on my blog for anyone interested:
https://vk3il.net/projects/pressure-paddle/

73

David VK3IL

Steven Weber
 

Very clever David.

 

I worked for a small start up out of collage where we made precision pressure measurement instrumentation and load cells.

 

I always wanted to make a lever paddle with strain gauges. There would be no physical movement of the lever, it would just respond to the pressure of pushing on it. These pressure sensors you found might work in that application too.

 

73, Steve KD1JV

 

 

All,

I've been experimenting with a new design for a no-moving-part CW paddle for SOTA that is based on pressure sensors rather than capacitive style. It was inspired by a similar design described in QST in Feb this year, but redesigned to require no battery and be as compact as possible. It weighs just 26g (including the cable), so will hopefully make a useful addition to the SOTA kit.

I thought it may be of interest as a complement to Steve's rigs. I've tested it with both the MTR2 and the Soda Pop and seems to work fine, but note the comments in the blog article of potentially needing a slightly stronger pull-up on the key lines.

I've written up the details on my blog for anyone interested:
https://vk3il.net/projects/pressure-paddle/

73

David VK3IL

 

VK3IL
 

Thanks Steve. Interesting thought on the strain gauge approach. I haven't worked with strain gauges, but I suspect these sensors may not be sensitive to x/y axis strain as they are contacts separated by a thin resistive membrane designed to be sensitive to pressure on the z axis. May be worth an experiment though as that would allow creation of a paddle with no exposed components.

73

David
VK3IL


On Mon, Apr 1, 2019 at 12:56 AM Steven Weber <steve.kd1jv@...> wrote:

Very clever David.

 

I worked for a small start up out of collage where we made precision pressure measurement instrumentation and load cells.

 

I always wanted to make a lever paddle with strain gauges. There would be no physical movement of the lever, it would just respond to the pressure of pushing on it. These pressure sensors you found might work in that application too.

 

73, Steve KD1JV

 

 

All,

I've been experimenting with a new design for a no-moving-part CW paddle for SOTA that is based on pressure sensors rather than capacitive style. It was inspired by a similar design described in QST in Feb this year, but redesigned to require no battery and be as compact as possible. It weighs just 26g (including the cable), so will hopefully make a useful addition to the SOTA kit.

I thought it may be of interest as a complement to Steve's rigs. I've tested it with both the MTR2 and the Soda Pop and seems to work fine, but note the comments in the blog article of potentially needing a slightly stronger pull-up on the key lines.

I've written up the details on my blog for anyone interested:
https://vk3il.net/projects/pressure-paddle/

73

David VK3IL

 

ohwenzelph
 

Ordering boards from ALLPCB.com, other than the size, 34mm x 63mm, was everything else left at the default values on the “PCB instant quote” page? I clicked 5 instead of 10 so I guess I have only ordered 5 instead of 10 for the same price. They gave me a $10 credit for registering with them. Have you ever used Hong Kong post with them instead of DHL? I am not in a hurry but would like the boards to arrive. They uploaded your Gerber Files zipped all at once no problem, but unzipped didn’t like them. Found the sensors on eBay for half of what amazon wanted (at the cheaper of bezo’s two prices). One place had $1.70 for the price of the pressure sensors but wanted $25 shipping! And yes, those diodes don’t look much bigger than black pepper flakes. Might need the microscope to see which end has the line on it.
Thank you for posting all of this information.
jerry aa1of

 

Allpcb is good but non-dhl shipping can take a long time 2-3 weeks or more. Dirtypcb is also a great place to try as well.
--
73

David

N8DAH

Shop.Kit-Projects.com

VK3IL
 

Hi Jerry,

Yes, leave all the other options on the AllPCB ordering page at default values. Changing any of them will likely increase the price substantially. Yes, their web site wants the gerbers as a single zip file.
I have use HK post as well as DHL. HK post takes MUCH longer, but I haven't lost anything yet. DHL is very quick (about 2 business days to my QTH from China). Yes the diodes are VERY small, just don't sneeze when placing them!

73

David
VK3IL


On Mon, Apr 1, 2019 at 11:10 AM ohwenzelph via Groups.Io <Ohwenzelph=yahoo.com@groups.io> wrote:
Ordering boards from ALLPCB.com, other than the size, 34mm x 63mm, was everything else left at the default values on the “PCB instant quote” page? I clicked 5 instead of 10 so I guess I have only ordered 5 instead of 10 for the same price. They gave me a $10 credit for registering with them. Have you ever used Hong Kong post with them instead of DHL? I am not in a hurry but would like the boards to arrive. They uploaded your Gerber Files zipped all at once no problem, but unzipped didn’t like them. Found the sensors on eBay for half of what amazon wanted (at the cheaper of bezo’s two prices). One place had $1.70 for the price of the pressure sensors but wanted $25 shipping! And yes, those diodes don’t look much bigger than black pepper flakes. Might need the microscope to see which end has the line on it.
Thank you for posting all of this information.
jerry aa1of

Steven Weber
 

David,

 

It might work if the sensor is “sandwiched” between the lever and a support. It should take very little movement of the lever and act much like a capacitive touch paddle. Could make for an interesting straight key.

 

I’ll have to order some of them and play around.

 

73, Steve KD1JV

 

 

Thanks Steve. Interesting thought on the strain gauge approach. I haven't worked with strain gauges, but I suspect these sensors may not be sensitive to x/y axis strain as they are contacts separated by a thin resistive membrane designed to be sensitive to pressure on the z axis. May be worth an experiment though as that would allow creation of a paddle with no exposed components.

 

73

 

David

VK3IL

 

 

On Mon, Apr 1, 2019 at 12:56 AM Steven Weber <steve.kd1jv@...> wrote:

Very clever David.

 

I worked for a small start up out of collage where we made precision pressure measurement instrumentation and load cells.

 

I always wanted to make a lever paddle with strain gauges. There would be no physical movement of the lever, it would just respond to the pressure of pushing on it. These pressure sensors you found might work in that application too.

 

73, Steve KD1JV

 

 

All,

I've been experimenting with a new design for a no-moving-part CW paddle for SOTA that is based on pressure sensors rather than capacitive style. It was inspired by a similar design described in QST in Feb this year, but redesigned to require no battery and be as compact as possible. It weighs just 26g (including the cable), so will hopefully make a useful addition to the SOTA kit.

I thought it may be of interest as a complement to Steve's rigs. I've tested it with both the MTR2 and the Soda Pop and seems to work fine, but note the comments in the blog article of potentially needing a slightly stronger pull-up on the key lines.

I've written up the details on my blog for anyone interested:
https://vk3il.net/projects/pressure-paddle/

73

David VK3IL

 

 

Joe Street
 

The devil is in the details with strain gauges ( as everything I suppose) .  I have a bag of the bare foils on kapton film which would be small enough to glue on a piece of aluminum the size you would likely want for a paddle arm.  Let me know if you really want a few and I'll mail them.  This would be an interesting project, but not trivial.  The signal levels from them are tiny and there is drift to contend with.  I was using a 24bit ADC with them and getting about 22 useable bits if memory serves.

Joe ve3vxo


On Mon, Apr 1, 2019 at 1:31 PM Steven Weber <steve.kd1jv@...> wrote:

David,

 

It might work if the sensor is “sandwiched” between the lever and a support. It should take very little movement of the lever and act much like a capacitive touch paddle. Could make for an interesting straight key.

 

I’ll have to order some of them and play around.

 

73, Steve KD1JV

 

 

Thanks Steve. Interesting thought on the strain gauge approach. I haven't worked with strain gauges, but I suspect these sensors may not be sensitive to x/y axis strain as they are contacts separated by a thin resistive membrane designed to be sensitive to pressure on the z axis. May be worth an experiment though as that would allow creation of a paddle with no exposed components.

 

73

 

David

VK3IL

 

 

On Mon, Apr 1, 2019 at 12:56 AM Steven Weber <steve.kd1jv@...> wrote:

Very clever David.

 

I worked for a small start up out of collage where we made precision pressure measurement instrumentation and load cells.

 

I always wanted to make a lever paddle with strain gauges. There would be no physical movement of the lever, it would just respond to the pressure of pushing on it. These pressure sensors you found might work in that application too.

 

73, Steve KD1JV

 

 

All,

I've been experimenting with a new design for a no-moving-part CW paddle for SOTA that is based on pressure sensors rather than capacitive style. It was inspired by a similar design described in QST in Feb this year, but redesigned to require no battery and be as compact as possible. It weighs just 26g (including the cable), so will hopefully make a useful addition to the SOTA kit.

I thought it may be of interest as a complement to Steve's rigs. I've tested it with both the MTR2 and the Soda Pop and seems to work fine, but note the comments in the blog article of potentially needing a slightly stronger pull-up on the key lines.

I've written up the details on my blog for anyone interested:
https://vk3il.net/projects/pressure-paddle/

73

David VK3IL

 

 

Carlos Tomazelli
 

Paddle Keyer pressure.
 
Guys,

I've done some experiments, the latest was touch see video https://www.youtube.com/watch?v=pJlQoSQMuec
For QRP it works fine, but for 80W RF we find flaws.
A great tip from our friend David VK3IL, these resistive cells are interesting.
I did some research and found another legal tip, using load cell weight 100 grams
http://wiki.robotmc.be/index.php/MorsePaddle
http://wiki.robotmc.be/images/1/12/MorsePaddleSchema.jpg
It seems interesting and functional, let's prove it.

Good experience at all.
 
A great start to the week, friend of Carlos PY2CSU

Joe Street
 

I think the pressure sensitive resistor design presented earlier pretty much nails it.  Simple lightweight and effective.  I doub't anyone would be abe to say all that about any strain gauge based design although I'm sure it could be made to work.



On Mon, Apr 1, 2019 at 2:08 PM Carlos Tomazelli <carlos_tomazelli@...> wrote:
Paddle Keyer pressure.
 
Guys,

I've done some experiments, the latest was touch see video https://www.youtube.com/watch?v=pJlQoSQMuec
For QRP it works fine, but for 80W RF we find flaws.
A great tip from our friend David VK3IL, these resistive cells are interesting.
I did some research and found another legal tip, using load cell weight 100 grams
It seems interesting and functional, let's prove it.

Good experience at all.
 
A great start to the week, friend of Carlos PY2CSU

Steven Weber
 

I used to help design and build instrumentation that would resolve a 15 mv Full scale signal from a load cell to 1 part in a million. In the late 70 and early 90’s. Yep, it wasn’t trivial.  Instruments I built were in use (and may still be) at all the government standards labs for calibration. Spent 15 years in the load cell industry. Our load cells were used to weigh  everything from gold to junk.

 

73, Steve KD1JV

 

The devil is in the details with strain gauges ( as everything I suppose) .  I have a bag of the bare foils on kapton film which would be small enough to glue on a piece of aluminum the size you would likely want for a paddle arm.  Let me know if you really want a few and I'll mail them.  This would be an interesting project, but not trivial.  The signal levels from them are tiny and there is drift to contend with.  I was using a 24bit ADC with them and getting about 22 useable bits if memory serves.

 

Joe ve3vxo

 

On Mon, Apr 1, 2019 at 1:31 PM Steven Weber <steve.kd1jv@...> wrote:

David,

 

It might work if the sensor is “sandwiched” between the lever and a support. It should take very little movement of the lever and act much like a capacitive touch paddle. Could make for an interesting straight key.

 

I’ll have to order some of them and play around.

 

73, Steve KD1JV

 

 

Thanks Steve. Interesting thought on the strain gauge approach. I haven't worked with strain gauges, but I suspect these sensors may not be sensitive to x/y axis strain as they are contacts separated by a thin resistive membrane designed to be sensitive to pressure on the z axis. May be worth an experiment though as that would allow creation of a paddle with no exposed components.

 

73

 

David

VK3IL

 

 

On Mon, Apr 1, 2019 at 12:56 AM Steven Weber <steve.kd1jv@...> wrote:

Very clever David.

 

I worked for a small start up out of collage where we made precision pressure measurement instrumentation and load cells.

 

I always wanted to make a lever paddle with strain gauges. There would be no physical movement of the lever, it would just respond to the pressure of pushing on it. These pressure sensors you found might work in that application too.

 

73, Steve KD1JV

 

 

All,

I've been experimenting with a new design for a no-moving-part CW paddle for SOTA that is based on pressure sensors rather than capacitive style. It was inspired by a similar design described in QST in Feb this year, but redesigned to require no battery and be as compact as possible. It weighs just 26g (including the cable), so will hopefully make a useful addition to the SOTA kit.

I thought it may be of interest as a complement to Steve's rigs. I've tested it with both the MTR2 and the Soda Pop and seems to work fine, but note the comments in the blog article of potentially needing a slightly stronger pull-up on the key lines.

I've written up the details on my blog for anyone interested:
https://vk3il.net/projects/pressure-paddle/

73

David VK3IL

 

 

 

VK3IL
 

Hi Steve,

That may work, but the pre-load in the sandwich would be critical. The sensor curve is highly non-linear with a huge change in resistance in the first 50g, so any pre-load would take the resistance down to a much flatter part of the curve and thus much harder to resolve low incremental pressures. Still worth an experiment though, so will be interested to see how it goes.

73

David
VK3IL


On Tue, Apr 2, 2019 at 4:31 AM Steven Weber <steve.kd1jv@...> wrote:

David,

 

It might work if the sensor is “sandwiched” between the lever and a support. It should take very little movement of the lever and act much like a capacitive touch paddle. Could make for an interesting straight key.

 

I’ll have to order some of them and play around.

 

73, Steve KD1JV

 

 

Thanks Steve. Interesting thought on the strain gauge approach. I haven't worked with strain gauges, but I suspect these sensors may not be sensitive to x/y axis strain as they are contacts separated by a thin resistive membrane designed to be sensitive to pressure on the z axis. May be worth an experiment though as that would allow creation of a paddle with no exposed components.

 

73

 

David

VK3IL

 

 

On Mon, Apr 1, 2019 at 12:56 AM Steven Weber <steve.kd1jv@...> wrote:

Very clever David.

 

I worked for a small start up out of collage where we made precision pressure measurement instrumentation and load cells.

 

I always wanted to make a lever paddle with strain gauges. There would be no physical movement of the lever, it would just respond to the pressure of pushing on it. These pressure sensors you found might work in that application too.

 

73, Steve KD1JV

 

 

All,

I've been experimenting with a new design for a no-moving-part CW paddle for SOTA that is based on pressure sensors rather than capacitive style. It was inspired by a similar design described in QST in Feb this year, but redesigned to require no battery and be as compact as possible. It weighs just 26g (including the cable), so will hopefully make a useful addition to the SOTA kit.

I thought it may be of interest as a complement to Steve's rigs. I've tested it with both the MTR2 and the Soda Pop and seems to work fine, but note the comments in the blog article of potentially needing a slightly stronger pull-up on the key lines.

I've written up the details on my blog for anyone interested:
https://vk3il.net/projects/pressure-paddle/

73

David VK3IL