Jury Designs

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...

Hi, Just a quick post showing the stability and accuracy of 2 separate voltage regulators working together. The mixer project requires a regulated positive and negative rail for the op-amps so I wanted to test how well they regulated when working together. For this I used LM317 and LM337 adjustable positive and negative voltage regulators. The basic schematic I drew up is shown below. Below are some tests showing the voltage drift over the course of an hour or so. As it was a quick test I had to work with the resistors I had on hand so don't pay much attention to the actual voltage but shown is the total of the negative 3 volt rail and positive 3 volt rail. Obviously in the final circuit the total will be 6 volts and not the 5.3 shown. I'll go into more detail in another post I just thought I'd share the results from this quick test. Justin

Hi, Recently I asked a lecturer what processor the OMRON PLC's generally used and all I got was a dumbfounded look and a who cares reaction. Fast forward a couple of months I purchased a used one off eBay and to initially program the unit I had to pull it apart. I'll go into more detail about that in another post but I thought why not take some photos and identify the main components on the board. I couldn't find any reference on the net as to what's inside one of these units so I thought some people out there might find it interesting. As expected ,however, there's not much to them. The main chips and their datasheets are: Renesas HD6437145 - Datasheet Cypress - CY7C1021CV33 - Datasheet - $6.94 Maxim – MAX3243 - Datasheet - $7.67 Renesas – R1LV0408CSA - Datasheet - $19.85 SN74LV14A - Datasheet - 72c Thanks for reading Justin

Hi, I've decided to finally get around to finishing this two channel mixer. I've done a post on using the OPA2134 op-amp so the next step is some VU-meters to monitor the gain levels. For this I've decided to use an LM3914 Dot/Bar Display Driver chip. I know there's the LM3916 which is more suitable for VU meters but I happened to have the LM3914 on hand and i'm only after a rough indication that the gain is at its maximum. The datasheet can be found here For the mixer the circuit will closely follow the typical application circuit from the datasheet shown below. There are a few things that we need to change. First of all the range in this example is 0V - 5V. Because this mixer will be USB powered and therefore 5V, we will run into problems with the signal hitting the rails of the op-amp and the LM3914 having to also operate at its rails so we need to change the range from 0V to 4V (which is pushing it). The other thing that we need to change is the LED c...

  The quality of the voltage reference is key to a precision multimeter so it was worth spending some time to run some simple tests on the MAX6341 to verify that it will be fit for the task of building a precision multimeter.         MAX6341 Key Features ·          Ultra-Low, 1ppm/°C Max Tempco  ·          Very Low, 1.5µVp-p Noise (0.1Hz to 10Hz) (MAX6325)  ·          ±0.02% Initial Accuracy (MAX6350)  ·          ±15mA Output Source and Sink Current  ·          Low, 18mW Power Consumption (MAX6325)  ·          Industry-Standard Pinout  ·          Optional Noise R...

Hi, I thought I'd blog some study/revision I'm currently doing for an exam. This won't necessarily be a comprehensive explanation of the topic, rather just the relevant formulas and notes that I'd personally create for myself when studying for an exam. This entry is on linear motion and uses the "Engineering Mechanics" book by "Val Ivanoff". Linear displacement , a vector quantity (distance and magnitude), is described as the position change of an object from one place to another along its path. The symbol for displacement is "S" and the SI base unit is m (metres). Linear Velocity is the change in position of an object which occurs in time or the time it takes to change from one position to another. The symbol for linear velocity is "v" and SI base unit is in m/s (metres/second). This is most commonly used when referring to the speed of a car. For example, "I'm currently travelling 60km/h sounds better than 16.7m/...

Hi, This is just a quick post showing my tests of the OPA2134 OPAMP from TI. Datasheet - http://www.ti.com/lit/ds/sbos058a/sbos058a.pdf I'm not sure whether or not I'll use this in the final design but as its touted as a "High Performance Audio Op Amp" I figured it's not a bad place to start. At around $7 AUD its not necessarily the cheapest Op Amp around. It's available in single, dual and quad versions but as I'm after individual control of the Left and Right channels, I chose the 2 channel 2134. Now to the breadboard! If you read the previous entry I explained how to setup a split power rail (and the reasons why you need one) to supply the + & - voltages used by the chip. Whilst not shown in this quick example, I used a TLE2426 rail splitter IC to supply +6V and -6V from a 12V power supply. I'll show the use of this chip in detail in another entry. Rather than go through the theory of the values used I've decided t...