HX890 Radio Power Clip

thingiverse

I'm a sailor, and my handheld marine VHF for my dinghy (Tits Akimbo), is a Standard Horizon HX890. A pretty good radio with WX, GPS, basic way points, DSC, etc, etc. (https://www.standardhorizon.com/indexVS.cfm?cmd=DisplayProducts&ProdCatID=85&encProdID=182D978C9908C3DD4EBE62DC0E44BFED&DivisionID=3&isArchived=0) The unit comes with a single base on which to charge, which I mounted in the sailboat. The radio can only get power to charge using this base, there are no covered power connections on the unit itself for charging with just a cable. I wanted a way to charge the radio while away in the dinghy as there could be times when I’m out for more than 8 to 12 hours. I could just buy another base, they are about $35 USD, but why spend a trivial amount of money when I could spend 20+ hours of time designing something, and besides, the base is a bit bulky and I wanted something smaller for in my dinghy lazaret. So here is my solution. Just a quick pedantic note, it always bothers me when people refer to cables or bases as “chargers”. The “charger” is a very specific circuit in electronic devices that takes in power, gives that power to the battery, and then stops giving the battery power when the battery is full. The “charger” (as part of the battery management system) is what prevents lithium ion batteries from exploding. While this charging circuitry can sometimes be external to the device (like 18650 Li-ion or NiMH household battery chargers) most of the time the “charger” is in the device itself. The HX890’s charger is internal, and the only thing needed to charge the battery is to apply 12v to the metal contacts on either side of the radio towards the bottom (See photos). The polarization of the 12v power is important, with positive being on the left side when viewing the radio, the side with the Push-to-Talk button. (again, see photos) The clip I designed simply slides onto the bottom of the radio, provides a path for getting power to the metal contacts, and provides sufficient friction so that the clip does not slide off accidentally. The power contacts in the clip are using two small M2x5mm screws. I literally salvage these off the floor, they probably came from an old HP or Dell laptop, and if you do anything with small electronics you probably have dozens of these just laying around. However, I'm including the link below on where to get some, but seriously don't spend any money, just start taking apart small electronics and you'll find some. The clip has a cable channel that will allow you to run a 2mm wire from the bolt to the base. Again, just salvage the wire from somewhere, you're not going to be carrying enough amps over this circuit to matter. Attaching the wire to the bolt can be a little tricky. I learned the hard way that soldering is not viable. The PLA will melt long before you can get enough heat into the screw to attach the wire. I used a technique where I simply fanned out the wire and screwed the bolt into the hole making contact. Play around a little bit with the depths of the screws to ensure good contact with the radio and the clips slips on easy enough. Once you can confirm that you have the contact between the wire and the screw, (seriously, if you don't own a voltohm meter, we can't be friends), then at the end, seal up the cable channel with some epoxy. This will lock everything in place. I have two variations on the clip design, 1.5 and 2.0. Version 1.5 simply provides cable channels to the bottom of the clip and you can wire in any 12v DC source and use whatever connector you wish (just make sure your polarities are correct) Version 2.0 is a bit more complex, and is the one I use. It is designed with a thicker base for accommodating a 2.1MM X 5.5MM DC barrel jack. I happen to have one of these I could salvage, but this one is a little bit rarer, so there is a link below and where to get them. The opening is 10mm so most surface mount connectors will fit. Rather than using any kind of locking nut, because of the tight space, at the end you can just epoxy it into the hole. In fact, the last step I would recommend once you get everything wired and tested is to fill up the void in the bottom of this version where the DC barrel jack is recessed and the bottom cable channel with epoxy. It will seal and lock up up everything. Print Recommendation: If you happen to have glow-in-the-dark PLA, printing this clip with that will make it easier to find in the dark while digging through a locker in an open boat in the rain. Version 1.5 I recommend a 30% infill, this will give the structure a lot of rigidity to hold the bolts to metal contacts and keep the clip from just falling off. The larger base on version 2.0 gives the structure quite a bit of rigidity on its own, so you can print with just a 20% infill. Additional Parts: 2x M2x5mm screws with thin heads (https://www.metricscrews.us/index.php?main_page=product_info&cPath=98_5_25&products_id=469) A couple of feet of 2mm stranded wire. 2 part Epoxy Optional: 1x Surface Mount DC Connector Jack, 2.1mm x 5.5mm with 10mm diameter. (https://www.twinschip.com/Panel_DC_Power_Connector_jack%20_Small)