Month: February 2018

Battery charger choice

Battery chargers for LiPo & LiFe batteries are a popular topic for discussion.

The one I chose is shown above. At 50W its not the highest power available but it charges batteries fast enough for me, and it was reasonably priced.

It is a very flexible charger, able to charge a wide range of batteries:

  • LiPo
  • LiIo
  • LiFe
  • NiMH
  • NiCd
  • Pb

It has a balanced charging connection for Li batteries of varying voltages & can charge all the battery technologies you are likely to come across.

A feature I particularly like is the ability to charge from mains or a 12v source. Just unplug the mains lead and plug in the DC cable, shown loose in the picture.

This means that if I have small portable batteries to charge and access to a car or other source of 12V such as a large bank of lead acid cells, I can use the charger for that.

I’ve changed the DC input and output connectors to PowerPoles to match the rest of my equipment.

I can’t comment on long term reliability, but will report any issues which arise.

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Pelicase alternative

Pelicases are widely used for Go-Boxes and protecting equipment on the move, and they are excellent, but not inexpensive.

At a trade show I came a cross a display of the MAX IP67 cases, which are made in Italy, and seem to have many of the characteristics of  Pelicases, but are a lot less expensive.

MAX430ARA-VUOTA-GRANDE

With IP67 rating they are waterproof and dust proof, and have an air  pressure release valve for when taken on a flight. One of their markets is Military use, so that suggests they are pretty rugged too, as does their promo video.

The feature they don’t have is the option of a metal frame to screw into the top of the large compartment for mounting a panel on. It does however look as though there is space to drill and insert small self tapping screws directly into the plastic, to mount a panel directly. Also, if your panel is fairly thick, the lid will keep it in place when closed and on the move.

Pelicases are glass reinforced while these are polymer only, so if your box will have to take a real hammering when closed maybe you need a Pelicase, but most Amateur use cases are not that severe.

Find out more at https://www.maxcase.co.uk

 

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Securing your Battery

Securing a battery into a plastic case can be challenging.

The most secure way would be to bolt some brackets into the box which would hold the battery rigidly in place. This may however break the waterproof integrity of the case, so is not ideal.

A method which I have found to be quick, easy and good enough, is to use strips of adhesive Velcro.

In the example shown, the case has curved corners between the sides and the bottom, so I’ve used some plywood as a standoff to create a 90 degree angle, held in place by Velcro.

I’ve then covered the side of the battery in contact with the box bottom with adhesive Velcro and stuck it down. When the box is in use and horizontal, the weight of the battery pushes down on the Velcro, and when the box is standing upright, the weight is taken by the plywood packing so does not stress the Velcro.

In normal use, this seems to adequately hold the battery in place. Dropping the box from a height on its left hand end might dislodge it, but that’s not a risk I feel the need to mitigate, given the use case I have.

If the battery does become loose, it can be easily Velcro’d back in position.

I put the battery against the side to take advantage of the bracing it offered, but it does make the box a bit unbalanced when carrying, so if I did it again I’d put the battery in the middle, and probably use a LiFe battery to reduce the weight.

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Particle Photon

The Particle Photon is a neat little micro-controller board with an STM32 ARM Cortex M3 micro-controller, a  Wi-Fi chip with on-board or external antenna, and  multiple digital and analoge inputs & outputs.

As you can see by comparison with the breadboard, its really small. I added an external Wi-Fi antenna for more range, but is not needed if your signal is strong.

particle1

To program you create a cloud account, link it to your device, and then program in the cloud IDE and deploy to your device. Dead simple!

particle2

Even simpler is the Particle smartphone app. Just link it to your device and you can read and set analogue and digital values for the IO pins.

The smartphone app reads from and controls the Photon via the Particle cloud. Therefore  when I’m standing by the board and pushing a button on my phone to make the light come on, traffic is going from my phone to the Particle cloud, then back to the Photon. Cool.

I’m hoping the traffic to and from the Particle cloud is authenticated and encrypted, but will be checking before I give it any serious use. I’ll do some packet sniffing with WireShark and also use an intercepting proxy with DNS spoofing to see how it fares against Man in the Middle attacks.

In the breadboard photo, the Green LED is connected to D0, which has been set to High using the App, and lo and behold, its lit up.

This makes it useful without any programming as by connecting TTL relays to digital pins, you can turn them off and on at the touch of a (virtual) button.

Interestingly, with suitable programming, you can link to the Amazon Echo, and control the outputs via voice.

 

 

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VHF/UHF Frequency Counter

When setting up memory channels for example for Satellite or Repeater use, its handy to have a quick way of making sure the transmit frequency and other parameters such as CTCSS are correct.

Nothing worse than failing to make contact and then eventually (when its too late) finding that when setting the CTCSS tone, you were one knob click off the correct one.

I find the Surecom SF-401 Plus a convenient and fairly inexpensive device for this.

Its light weight but doesn’t feel too fragile, has a rechargeable battery with auto turn off feature, and while a colour display isn’t essential, having it makes the counter nicer to use.

Its not a tank, like my OptoElectronics Scout, but that doesn’t do CTCSS and might be finding its way onto e-bay soon.

scout

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Connecting Batteries

Having moved to using LiFe batteries for lightweight portable power, I needed to make them compatible with the PowerPole connectors most of my equipment uses.

The 4200 batteries come with 5.5mm bullet connectors, so the easy way was to buy a bullet to banana plug cable from the same supplier as the battery and replace the banana plugs with PowerPoles. These cables have very flexible insulation, so are great when in use.

I noticed that an insulation gap appeared where the 5.5mm bullet connectors joined together, so to keep things safe and stop the connectors coming apart inadvertently, I covered the join with heat shrink tube and  I’ll keep an eye on it.

bulletcon

An alternative is to connect the PowerPoles directly to the battery.

plug1

You need to be very careful not to short the battery cables while doing this, and do take off any metal rings on your hands, as if you short via a ring you may lose the finger.

fingerringburn

I use 30A PowerPole inserts and you may find that the battery conductor is too big to fit. As I am not needing more than 30A, I just trim the cable strands off until they fit snugly, I also put a bit of thin heat shrink from the cable to the crimp part of the PowerPole.

You might be wondering where the fuses are, and they will be in the circuit which is connected to the battery. Putting them on each battery lead would have been clunky, and if reasonable care is taken, its unlikely that there will be a short across the PowerPoles on the battery.

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Power Distribution

When building Go Boxes, I used to find connecting together the power distribution cables for the equipment a hassle, until I found these Wago connectors in an electrical distributor. They are widely used in the UK for house lighting wires and come in 2,3 and 5 conductor capacity.

As they are quite small, I bought a box of 5 conductor units with the view that even if I only need 2 or 3 for some applications, they don’t use up much space, and if I need more connections than I thought, they are available.

power1

The connectors are rated at 32 Amps and capable of taking up to 4mm square cable, you just lift the lever and slide in a stripped cable, then push it down for a secure connection. Use one for +ve and another for -ve & job done. A decent length of the insulation slides into the connector so shorting to the metal panel below is not an issue.

The main picture shows a project I’m just getting started on with the first wires connected, and the pic below gives the part details.

Power2

I also use a lot of this Acrylic foam tape which is very sticky, holds well and doesn’t lose its grip with time.  While described as foam, the material is more a clear plastic somewhat stretchy gel, a couple of mm thick with adhesive either side. This helps if the surfaces are not completely smooth/parallel.

Its perfect for sticking these Wago connectors down, and for mounting other lightweight parts.

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