Tag: Workshop assets

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CCTV System with remote camera over WiFi

Some head scratching but a working solution

I had a request for help with a CCTV system where the owner wanted to add a remote camera to an outbuilding with no cable route possible. This should have been a JSN job (Just Say No) but I’m always up for a (steep learning curve) challenge. After some investigation (back of a napkin sketch and a quick Google search) I opted for a 5GHz WiFi bridge and thought the job was going to be easy. JSN jobs are like that but you have to be conscious that they come configured with inbuilt mission creep.

The WiFi link was a 24V power over ethernet (PoE) system. The existing three cameras were 48V PoE and the additional camera was to be the same.

Here is the final configuration. The red lines are PoE and the blue lines are just basic CAT5 unpowered connections.

The NVR is a SPRO four port device with 48V PoE on all ports. To save cabling the owner had used a PoE pass through switch so two cameras could share the same cable running back to the NVR. The existing third camera was a direct feed from the NVR. I was quite impressed with the pass through device. It has the capacity to allow four cameras to share the same PoE NVR connection.

Back to the plot … Adding the fourth remote camera using a bridge would have been simple if the bridge was 48V PoE powered but it was 24V PoE. The remote location therefore needed two PoE inserters – a 24V one for the bridge and 48V for the camera. The LAN ports on the two inserters just need connecting together to complete the link. The NVR ‘sees’ the remote location as a locally connected camera.

Something to note. The bridge (KuWfi) as delivered has two IP addresses configured, 10.1.1.253 for the Master location and 10.1.1.100 for the Slave location. All the cameras are allocated 10.1.1.x IP addresses on the NVR. The NVR also has an internet connection for remote Smartphone viewing.

KuWfi provide an application to configure the two bridge units. I spent a long time trying to work out how to get this to respond to either device. In the end a light bulb moment reminded me that a previous Chinese sourced product had the same issues. I had traced this to a Chrome related problem (which I never solved) and found the Application would only work using Edge. The same happened this time. Using Edge got me into both units without a problem. Note that you have to set your host interrogating computer to be on the 10.1.1.x domain.

There is a signal strength graphic on the Slave GUI which is very useful. You can connect your computer LAN port to either the Master or Slave 24V injector LAN port and request either of the two addresses (10.1.1.100 or 10.1.1.253) from either end of the link

Just think how much simpler it would have been if the bridge also ran from 48V …. maybe someone produces a 48V to 24V PoE step down converter ? Or maybe I should just stick to the things that I pretend to know more about … and JSN.

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Rotring 300 2mm clutch pencil modification

A replacement lead pusher/ sharpener button

I am a great fan of the Rotring 300 clutch pencil that takes 2mm lead. Together with Sharpie markers these make good shirt pocket workshop assets. The pencil has one weakness … the useless ‘sharpener’/ lead pusher that always keeps dropping out, rolling under something/ getting lost, all of which render the pencil frustratingly useless.

When this happens my solution is to model and make a replacement pusher albeit without the sharpener facility. I already have a Staedler Mars sharpener (#502) which is a far better sharpener.

The choice of how to make the new pusher is either a very luxurious metal replacement or a cheap and easily replaceable 3D printed one. Both work well and below are the essential dimensions. Note that these are correct for a metal replacement but for a 3D printed one you might need to tweak the 4mm and 5.5mm diameters to suit your printer accuracy (4.25mm and 5.45mm on mine).

The 3D printed version has a natural friction that retains it in place. The metal one is a bit too perfect and needs the open end slightly distorted (crushed) to help retain it.

The pencils, spare leads and the sharpener all available on Amazon.

The final shirt pocket recommendation is the twin tip Sharpie marker. These are really useful for marking out.

Sorry that wasn’t very interesting but someone somewhere might be grateful of not having to waste too much time down on their knees looking for the useless end button.

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TPL5110 as a Monostable

Low Quiescent Standby Current Power Switch

After finishing a recent project I had a heap of resistors that had been used as select on test parts and now needed sorting and storing correctly. I found a design on the web for a simple Arduino based autoranging resistance meter. I prototyped the measurement circuitry for this and it worked fine. I wanted the power to the device to be from a battery source and to have this turned on via a push button switch and to auto time the ON period and return to standby.

My immediate thought was to use the ICM7555 CMOS equivalent of the ubiquitus 555 as a monostable but although manufactured in CMOS technology it does have a relatively high standby current. Some web research led me to the Texas Instruments TPL5110 which can be used as a monstable triggered from a push button. The device has an incredibly low standby current of a few uA. To use the TPL5110 as a monostable is quite simple. The EN pin is tied to ground instead of to supply. The resulting section of circuitry is simple and is shown below.

The push button sits across the U$7 (supply rail) and U$8 (trigger) terminals and the ON period of the monostable operation is adjusted by the R22 trimpot. A 10 second ON period needs around 10K. Ignore the use of parallel resistors (R21 and R18) as this was to allow my PCB layout to use either a through hole part or SMD part. The switching FET for the supply is a commonly available P channel part. The particular part chosen (DMG3416) has a very low ON resistance. Note that the TPL5110 cannot be used over 5V.

The result is very legant and simple. The standby current was so low I struggled to measure it.

Note that Adafruit has a ready made module that uses the TPL5110 but this is configured with EN permantly connected to the incoming supply. In this mode the device is intended as a timing reference to turn projects ON and OFF at regular intervals in association with feedback from an associated microcontroller (via the DONE pin). If you look at the Adafruit PCB layout you will see that you will need some delicate hacking to get at the EN pin as this is linked to the incoming supply under the TPL5110.

More will follow on the completed Resistance Meter project which has an OLED display and 3D printed enclosure.

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Modifications to a FeelTech FY6900

Some useful tweaks to the frequency standard and power supply

The FY6900 is a very versatile while relatively low-cost function generator.  It has two independent signal sources each with a plethora of output waveforms and it also provides a frequency counter facility. The version I bought was specified to 60MHz and the cost was sub GBP100. It has a somewhat clunky user interface with a single-entry knob for settings but this can be supplemented with a USB PC graphical interface. While not the most sexy of instruments I have grown to appreciate it as a really useful cost effective addition to my electronics workshop.

While working on a clock related project, I had the feeling that the FY6900 displayed frequency did not necessarily accurately match other sources. As the unit does not have an input for an external frequency standard this made cross checking analysis difficult. Download the PDF below to read my notes on fitting an external reference input socket and also upgrading the 10MHz internal reference.

Modifications to the FY6900 Waveform GeneratorDownload

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Further Diesel Heater Update

Results from fitting an electronic fuel pump

As mentioned on a previous post, I came across a YouTube video regarding a UK source of an electronic replacement for the mechanical pump for use with my 3kW diesel heater. I ordered one of these and have just installed it.

James Browning does not have a website. You send him an email to the address below and he sends you the details of his product. Note that you need to copy his address into your messaging app as the link below is an image not a URL. This affords him some protection against spam.

Installation of James’ box is straightforward with copious notes and videos to assist. Connections are simple – +12V, 0V and the two old wires originally going to the mechanical pump. You need to route the fuel feed via his box and then before running the heater you need to bleed the air from the pipework. There is a handy little switch in the box to help do this.

There is a knob on the box that alters the fuel mix which you can tweak with altitude. This is relevant if you are touring in a mobile home but not for my installation heating the workshop. The box as delivered has the fuel mix set to sea level operation and as I am at 90m asl I left it untouched.

So what have I noticed ?

First of all the old ticking noise has gone and the burner noise is more even. Major plus.

With the mechanical pump I had to put a metal plate against the wall to stop the soot staining the brickwork. Clearly the burn as it was was not correctly balanced to have caused this. With the new electronic pump all I have is condensation dribbling down the plate (it is freezing cold outside) so the burn is more efficient.

I can now burn our domestic heating oil (kero) as the fuel does not need to have any lubrication content as it did for the mechanical pump. Currently in the UK domestic heating oil is around GBP0.70 per litre and road diesel is GBP1.60 so a direct net saving amortising the cost of James’ unit.

Conclusion therefore : -no ticking, more efficient burn, lower cost fuel leading to an overall fast investment return and ultimately a net saving.

So far I am very pleased with the upgrade to my heater and I wish James every success with his innovation.

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