External battery pack to extend the battery life on wireless tags

A game of tag anyone ?

I have installed a network of low cost wireless sensor tags to monitor our homes here in the UK and also in France. These are really useful little devices that measure temperature, humidity and motion such as a door opening. 

They store their readings and can be interrogated via the Internet to see a profile history.   They also have limit alarm trip options that push messages to email to let you know if anything untoward is happening.  The product website is here.

Tag device
Image of a tag device

As examples of their use, here in the UK we have one fitted inside our freezer to check that the temperature is within limits.   Should the freezer fail or the door be left slightly ajar we get a message. 

In France we have one installed inside the spa pump cabinet to check the temperature over winter to check that the pipework does not see freezing temperatures.  This works in conjunction with a greenhouse tubular heater that is also in the spa cabinet wired to a frost stat set to 5C degrees.  If the temperature drops the pipes are protected by the heater coming on.   If the AC mains fail the heater will not come on and the sensor tag warns us to ask the neighbours to visit and check the electric distribution panel as we do experience frequent power outages.

Under normal circumstances the tag internal CR2032 battery will give a reasonable battery life approaching 12 months.  These are not normal circumstances however and due to COVID we have been unable to visit for over 12 months.  As a result all the tags at our house in France have dead batteries.  Their use inside freezers and outside in the cold degrades the battery life achieved. This got me thinking about fitting a larger battery pack to the tags in France to help longer battery life monitoring while we are absent.

My solution is not elegant but functional.   I have wired an external battery pack containing two AA batteries to the tags.   The battery box is a commercial item and is available in packs of five on EBay.  They come fitted with an ON/OFF switch and more than enough cable to connect to the battery contacts inside the tag. 

The tag case can be sprung open with a fine screwdriver or wood chisel and the PCB removed.   The dead battery can be slid out of the PCB battery holder. There are a string of five module probing lands at the foot of the PCB and after some checking I discovered that two of these are connected to the battery holder contacts.   The external battery pack wires can be fed into the case via a 3mm hole in the top edge.   The wires then pass through the old battery holder down to the bottom of the board and are soldered in place.   The tag is re-assembled, batteries fitted and switched on.  The tag will bleep if all is well.

How to wire the external battery pack
Internal view of the tag and how to wire the external battery connections

This electrical modification works but it is physically a bit gangly and scruffy.   A few minutes on Fusion 360 produced a simple 3D printed holder to contain the battery pack and the tag.   This has a slot so the temperature sensor is not obscured and a sprinkling of holes to allow physical mounting as appropriate.

Fusion 360 pictorial view of the tag and battery holder
Fusion 360 pictorial view of the tag and battery holder
Final assembly of the battery pack and the tag
Final assembly of the battery pack and the tag. The dot on the battery pack is a retaining screw.

In theory this modification should dramatically improve the operational life of the tags between battery changes but time will tell whether it is borne out in practice.

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3D printed multiple punch holding tool using Fusion 360 Parameters

Using Fusion 360 Parameter Functions on this useful tool

I was pointed to this punch holder idea by a friend.  It was shown on HomeMadeTools.net and conceived by Andy Foale.   

Here is the link to the original post : –

https://www.homemadetools.net/forum/multiple-hand-stamp-helping-hand-65882

I thought it might be practical to make it as a 3D printed device and with a bit of guesswork came up with a first pass design in Fusion 360.   This was based on my set of punches which are 6.4mm square (1/4″) and 58mm long.   The design printed in PLA without any problems and the finished punch holder worked fine.  It uses one of my printed knobs as mentioned in another post.

3D printed punch holder per Andy Foales
Fusion 360 pictorial view of the finished punch holder

The success led to requests from others who liked the 3D print concept but had different size punches so needed the design tweaked to suit.

This looked like a good excuse to re-familiarise myself with Fusion 360s Parameter functions.   In short these allow you to program interrelated dimensions in a design through a series of basic algebraic functions.   The end result is a design that is fully flexible on the size of the punches to be used and the number of punches that might be judged needed as the maximum ‘word’ length.

The Fusion file is here in a ZIP file

punch holder v5

The Fusion file includes the holder, the clamping bar and the knob body.   You will need a short length of M6 threaded rod and a M6 nut to finish the knob.  The file is configured to 6mm punches, 63mm long but you can edit using Parameters function under Modify.  Clearly once you have the Fusion file you could run also run a CAM program and CNC cut the punch holder.

I am afraid this is a Fusion 360 file only.   If you aren’t a Fusion user (why not ??) and you want a STEP file creating to your punch sizes then email me and I can run it for you.

As stated in the original article, the kerning of the letters is defined by the punch cross section.

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Home made knobs without knurling

I always used to make customised knobs in metal which had a knurled body with a piece of studding screwed and Loctited in place.   It was good knurling practice and they looked fine until 3D printing came along.

I now have a variety of ‘styles’ for knob bodies modelled in Fusion 360.  These have a hexagonal profile recess together with either a threaded hole or  clearance hole modelled into them.   A nut is Loctited onto the thread and then the thread with the nut in place SuperGlued into the 3D printed body.

As usual I’m all for an easy (a.k.a. lazy) way of doing things …. here is a Fusion image.

3D printed knob
Fusion modelled image of a 3D printed knob

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Milling vice stop for non grooved vice jaws

Another Job Ticked Off

There are a number of lower cost CNC milling vices (vises) available on the market that do not have jaw geometry with grooves for tooling fixtures and vice stops.   Admittedly their jaws could be machined to add this facility but many of these vices have hardened jaws which presents more of a problem.

My CNC vice came from the UK supplier ARCeurotrade and is from their ARC Versatile SG Iron Milling Vices range.   I have the 100mm wide jaw version and the jaws are  just over 11mm (7/16″) thick.

I have a simple plate that acts as a stop  that is flush with the end of the jaws.  This makes use of existing holes in the vice body but often I need to have a stop internal to the jaw footprint.  Juggling then results with all manner of Heath Robinson solutions.

My design is simple and clamps onto the thickness of the jaws.   

There are two M3 clamping screws and there is enough adjustment on these to allow a parallel to also be gripped should it be needed.

CNC vice stop showing clamping onto the vice jaw and also when used with a parallel
CNC vice stop showing clamping onto the vice jaw and also when used with a parallel

I allowed for two positions for the stop rod and the rod is held with a grub screw in each.   There is a central burr clearance neck on the rod so the grub screw does not damage the surface of the rod and make removal difficult.  Clearly the rod could be simplified to have just a single fixed position.

The rod can have rounded ends or it can have ball bearings glued into a cavity on each end of the rod.   The ball bearings would give a higher resilience to damage.

So nothing really complicated or rocket science with just an hour or so of workshop pleasure.   The size can be adjusted to suit your vice jaws and the material can be whatever is in the junk box.

Here is a link to the 2D drawings that were created in Fusion 360.

CNC vice stop Drawing v3

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Burgess BK3 replacement lower blade guide

Burgess BK3 Final Modification – Lower Blade Guide

This is the final piece in my Burgess BK3 bandsaw upgrade jigsaw.   Having successfully replaced the top guide with a double bearing assembly my attention turned to the lower guide.  Using the same principle as the upper guide I came up with the following assembly.

Burgess BK3 bandsaw replacement lower guide assembly
Stylised Fusion 360 image of the replacement lower guide assembly on my Burgess BK3 bandsaw

This seems to work well and is straightforward to implement.   The bearings are standard 1/2″ size parts from Bearing Boys.   These need a small brass bush to mount them on the sliding brass blocks.  The blocks need a single M3 washer to space the bearing from the block and the body.

The blade pressure roller is made from silver steel and can be heat treated to improve wear from the blade edge.

The mounting bracket arm picks up on the original M5 mounting screw concept.  The bracket could be milled onto the main body as a CNC operation but the two part assembly works fine and is very rigid in operation.

Here is a set of drawings for my BK3 lower guide assembly

The link below is a complete set of notes and drawings pulled into one ZIP file to cover all the modifications I have done and separately document in my blog and other author’s notes that I have come across.  I hope that helps.

Updated file link to BK3 Modifications v2

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