Monday, 21 February 2011

The Last Parts

I completed the sensor connection PCB this weekend. I need to cover it with heatshrink to protect it but I need to test the full system before I can do that. Here it is connected to the gun complete with curly cable leading to the sensors:

Here is the complete assembly:

To test the system I need to construct another Milestag PCB. As mentioned before I bought 4 of these so I used my PCB jig to help me populate the boards:

This device holds multiple PCBs, allowing me to place components. When populated, a foam covered board is placed over the components and clamped in place. The jig then rotates to allow the components to be soldered whilst the foam prevents them from falling out:

Here are the completed boards:

I intend wire IR LEDs and trigger switches to the boards so I do a quick test. Before I can do anything with the remaining boards though I need some more gun housings, and for that I need my own RepRap......

Sunday, 6 February 2011

Completed Sensors

Today I attached the two sensor housings to the new RJ10 PCB I made. Here is a detail of the junction PCB showing the two sensor leads attached with tie wrap strain relief:

Here is the assembly showing the two sensors attached:

I decided to attach the sensors to clothing with velcro. This allows me to flexibly configure the sensor positioning as required. I bought some 50mm velcro and stamped holes in it to allow me access to the sensor screws.

I've also designed a small PCB to hang from the gun to allow me to connect a RJ10 curly lead to the sensors:

I just need to make this and the gun is complete.

Thursday, 3 February 2011

Sensor Connections

I've been trying to find the best way to mount the Milestag sensors to a headband and connect them to the gun.

I've decided that I'm going to mount a loop strip of velcro on a baseball cap or elastic headband and attach hook velcro to the back of the sensors. This gives me the most flexibility for sensor placement.

I've been unhappy with the way the sensors connect. They are traditionally soldered in parallel with a connection to the gun. I had concerns about the reliability of this as soldered connections break when flexed.

I decided to compromise and designed a PCB to connect two sensors to a RJ10 socket. Why RJ10 when others are using RJ11? Because RJ10 curly leads are available for less than 1UKP and these are ideal to connect the sensors to the gun.

Here is the headband sensor schematic:

It's very simple. I intend to place it in a small, velcro mounted box.

Here is a set of 8 PCBs ready for cutting and drilling: