Tormach Tool Height Caliper 3V Battery Modification

Background

As part of my purchase package of the Tormach PCNC440 I ordered their granite block and height caliper.  This meant I could measure and set tool heights directly into the tool table on PathPilot via the caliper USB connection.  See the image below which shows the granite block, caliper and the associated dongle box.

This concept works really well and saves manual entry typo errors when measuring tool lengths.   I have found one problem however and that is the caliper eats batteries at an alarming rate.   These are CR2032 button cells which are not dramatically expensive, but the cost does start to add up. There is the added frustration of the caliper potentially not functioning at a critical moment when a new tool needs to be measured.

It struck me as strange that a device talking via USB should be dependent on a battery when 5V is available from the USB interface.   The fact that this did not happen suggested to me that the connection from the interface box to the caliper did not have through continuity of the 5V supply.   This wasn’t surprising given that the caliper runs from a 3V cell.

Investigation

I connected the caliper via a standard USB cable directly to a variable power supply connected onto the 5V power pin on the USB cable.  Varying the power supply from 0V to 5V showed that the caliper would work quite reliably over a range of 3V to 3.8V but above this the display would blank or just show 8888 at high intensity so masking the actual reading.

I found a couple of 1N4148 signal diodes in my component stock and put them in series with the 5V feed from the power supply to act as a series voltage drop.   This brought the working voltage delivered to the caliper back into the 3V to 3.8V range where it functioned without any problems.

Implementation

So the question was now as to how to implement this modification elegantly ? ….

Be warned that the modification to be described involves a change to the USB dongle box supplied with the caliper and as such will invalidate any warranty.   Mimic what I did at your own risk.

The dongle box has four screws on the bottom cover and removing these reveals the controller pcb.   Take care not to loose the three blue switch activator rods in the process.  On inspection of the pcb, the USB cable entering the box has all four standard USB connections but the cable exiting to the caliper has the 5V lead (red) disconnected.

I found a pin quite close by to the output lead that was marked 5V.   This was a possible feed for my two diodes.   On measuring this I found it was at a lower voltage than expected suggesting that there was perhaps some circuitry between this point and the incoming 5V.   I therefore chose to ignore this and looked instead to the input connection cable.   I found the +5V connection (red) as it connected to the pcb.   I connected the two diodes in series to this cable termination and then ran a connecting wire (orange below)across the board to the 5V output (red) cable which was previously not connected.

These modifications are shown below albeit with hot glue over the diodes and connections.

Modification to Tormach digital caliper dongle box

This completed the modification.  I checked out all the voltages while the pcb was still outside the box and also checked the caliper was still working.   I replaced the pcb back into the box and screwed the lid in place.

One final thing I did which is not necessarily essential but felt like a good thing to do, was to put a tantalum capacitor across the former battery contacts in the caliper battery compartment.   This would act as decoupling should there be any ripple on the new supply to the caliper.  See the image below.  Note that the tantalum capacitor is polarised and its + lead goes to the former + battery contact (on the right as shown below).

While this is a potentially useful thing to do, it has the disadvantage that you cannot put a battery in the caliper if you want to use it ‘off line’ when not connected to a USB port.   You could however plug it into USB charger via the dongle lead.

The other minor thing I did was to fit a small cable tie to retain the caliper connector in place as I found it easily become disconnected.

On putting the setup all back together, the caliper was working well with a nice contrast to the LCD display.  Tool table updates work just as they did before so no issues there.

If you do this modification you might want to experiment with different diodes or the number of diodes  needed to the drop the voltage from 5V to within the caliper normal voltage range.   Note that you need to use small signal silicon diodes which will have around a 0.6V voltage drop per diode.   Don’t use Schottky diodes as these generally have around 0.2V and so you would need at least 3 times as many to achieve the same overall voltage drop.  You could try LEDs as they all seem to have different voltage drops but they tend to need a high drive current which if this is the case, makes them unsuitable for this application.

You could of course go really elegant and build a small integrated power supply chip into the dongle box such as the AMS1117.   These are available in various fixed output voltages including a 3.3V version (which is popular for Arduino projects and available from Amazon). You can also buy a ready made 5V to 3V module based on the AMS1117 from Amazon.  I like the AMS1117 and used the 1.5V version in my power supply modification to the Shumatech DRO systems.

Here is a printer friendly (and slightly updated) version of this article : –

Tormach Digital Height Gauge Modifications

The Small Print Again

I repeat once again that this modification will invalidate your warranty on the caliper but it will save you the cost of batteries.

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Magnifier Lens Scratches and Polywatch

Working on small items requires me to use optical magnifiers such as the Rolson one with swap out lens.   These inevitably pick up scratches and other marks.

I recently bought some Polywatch polish from my clock parts supplier to polish a plastic clock dome which was looking pretty rough.   Polywatch transformed it to the point of where it looked almost new.

You can buy it on Amazon.

Today I tried Polywatch on my favourite Rolson Headmagnifier lens and I can now see what I am doing once again.  Worth remembering.

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The Power of Fing

While struggling to sort out the network folder issue with PathPilot v2 I mentioned that I could ‘see’ the Tormach and ping it.  One of the readers asked how I managed to find the IP address of the Tormach when it was automatically allocated by the server under DHCP ?

OK I am far from Cisco qualified so the next bit is how I see things work.  When a new device is added to the network for the first time you can either allocate a fixed IP address manually or let the server do that for you.  If you are a bit nerdy like me you might prefer to have a nice ordered manual list of all your main devices.   There is a slight danger that with fixed addressing you can drop the ball and allocate the same IP address to two different devices.   This is not good for the network and leads to smoke coming from ears.

DHCP takes the problem away.  Simply plug the new device into the network and it will talk to the server, get a IP address allocated and off you go.

The server keeps a register of which devices are active and generally will leave the IP address it has allocated unchanged between switch on uses.  It is a simple easy way to do things particularly for the non IT user.

To find if a device is live on your network you can send a ping command to the IP address of the device you are looking for.  The device will respond back and you know all is well.

BUT … if the device has been added using DHCP you will have no idea what the precise IP address of the device is.   So how can you ping something that you don’t know ?

There are lots of geeky commands to solve this problem but there is also a wonderful little App call FING.

FING can be loaded on desktops or portable devices.   When you run it up it sniffs the network and gives a listing of all the devices on the network with their associated IP address.   It also lists devices that have been seen on the network but not currently active.  You can tag names to each device and add icons for similar device types. Here is one of its screens

But that is just the start ….. it gives you the MAC address of each device.  MAC address is a unique number embedded in a network device by the manufacturer.   It is in essence a serial number.  The MAC addresses from a manufacturer will be similar looking so you can identify a device source.

On my wifi system I use MAC address filtering as extra security.  When a friend comes round and needs to log onto my network I can immediately see the device trying to get on but being blocked.  I can see the MAC address of his device and add it to my white list.

So back to the story.   I had loaded PathPilot version 2.0.0, enabled DHCP and connected to the network.  Fing immediately saw the Tormach and it was clearly communicating within the network.   This meant the problem was not network related but something in the Tormach not advertising the shared folder properly.

I thought that was going to be a short explanation post and look how long it ended up.   Short story – FING is a great app.

(BTW I have no connection, affilation, financial involvement etc with Fing.  I just like to tell people about what I regard as really useful apps).

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Leaking compressed air components and Loctite 577

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To aid distribution I sourced locally a 4 port manifold with an in and pass through in line.   This gave me a couple of spare ports for future expansion.

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A quick scan on the web and it seemed that Loctite 577 was recommended.  RS had it in stock and it was a revelation to seal the threads.  You just squeeze a thin ring of 577 around the thread and screw it home.  Job done ….. but maybe they won’t ever come apart again …. well that’s a problem for another day.

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