Jury Designs

Hi, For the last month or so I've been involved in arcade machines which all came about from inheriting an old 1979 Williams pinball machine that was long overdue for restoration. This is a big project as the whole machine needs to be sanded, filled, painted etc. but electrically it is in terrible condition as well. I'm currently in the process of re-doing the driver board in Altium because, as you can see below, the one in the machine is well and truly past it! I've nearly finished the board in Altium (shown below) and will be getting it manufactured soon. On top of this project I have also been designing and building a cocktail arcade machine for my partners 30th birthday party. I'll go into more detail regarding these projects in future posts but today's topic is on virtual pinball machines. My partner wanted to visit a local arcade shop so she could price an arcade machine similar to the one above and whilst there I noticed the full s...

Hi, Here's an excerpt from a report I completed on rapid prototyping. This section was on differential cooling and an easy way to overcome it. I thought some might find this useful when 3D printing at home as warping is a common problem. Differential Cooling Problems A common and often ignored (or accepted) problem with most 3D printers on the market is print warping. The cause of this problem is differential cooling. As can be seen in the following image the PLA plastic, when its extruded, is at a temperature of 116⁰C. The extruder itself hovers around the 200 - 200⁰C mark. The PLA sets quick when it’s on the print bed hence dropping from 116⁰C to ambient almost immediately. As the extruder performs its multiple passes, building up the levels, it continually adds hot layers of PLA on the set layers. In other words the PLA is continually heated and cooled. To overcome this many manufacturers have a heated print bed to try and keep this PLA at a constant temperature. In p...

Hi, I've got a few different projects going on at the moment that are all USB powered so I thought I'd do some measurements of the USB supply noise and try some ways of improving it. Initially I added bulk capacitance, 4400uF, to reduce the noise. This worked but obviously isn't really a solution particularly when the USB 2.0 standard specifies a limit of 10uF in parallel with the supply line to limit inrush current. The specification states that bulk capacitance can be used if a soft start method is implemented so that the inrush is not exceeded. This information comes from an FTDI application note ( found here ) and in this they show an example circuit for filtering the supply line. This circuit consists of a few capacitors and a ferrite bead, specifically BK0603HS330-T ( Digikey link ). I don't have any of these on hand but I thought I'd try a couple of inductors that I have. Specifically the B82141A 33uH( Digikey Link) and 77F1R0K 1uH ( Digikey Link ...

Hi, I was looking at the small solar panel car battery maintenance charger I bought awhile ago and thought, how useful would this be to charge a mobile phone. So I did some tests. As can be seen above, the specs of this panel are 12-16VDC, 4W and 300mA. I put together a quick 5V USB charging circuit on a breadboard following the typical application from the 7805 datasheet. Above shows the solar panel charging a mobile phone at a measly 171.3mA. With the 7805 linear regulator the input current must equal the output current therefore, following Ohm's law, the input power is always higher than the output power and the higher the difference in voltage, the worse the efficiency will be. Output = 171.3mA @ 5V - 5V * 171.3mA = 0.856 ~ .86W Input = 171.3mA @ 12V - 12V * 171.3mA = 2.055 ~ 2.06W η = Output Power / Input Power η = 0.86W / 2.06W = 0.417 ~ 42% efficient Now, out of interest, lets examine the thermal properties. The LM7805 datasheet specifies the juncti...