This was a relatively simple design to digitize breathing belt sensor signal and send the data to a computer. The nice feature was a wireless Bluetooth interface to the computer. I used an existing Bluetooth module in this design and wrote Java test program to receive the data. The software was developed by the client who was a SW programmer.
This tag combined the functionality of an RFID tag operating on 433MHz under 18000-7 protocol and a proprietary RTLS (Real Time Locating System) functionality.
For this product development I completed the hardware design including component selection, schematic capture, PCB layout, firmware architecture, initial prototype assembly and testing.
It was a challenge to make the 18000-7 and RTLS functionality coexist. There were number of timing conflicts that needed a solution that would result in low power while maintaining responsiveness.
I was a member of the firmware development team. I acted as the scrum master and also developed some of the code.
This device fit inside a machined metal tube to be lowered into natural gas wells with pressures up to 20,000 PSI and temperatures to 150ºC. It recorded pressure with the accuracy of 0.021% F.S. (Full Scale) and resolution of 0.0003% F.S..
I designed it this device with a 24 delta sigma converter. Careful calibration procedure was used to achieve the required accuracy.
I completed the design of the electronics, prepared schematics PCB and completed the firmware for this device.
This was a very nice project to build an isolator for industrial machines between the sensor side and output control.
It fit into a small DIN rail mounted enclosure and it had to operate at an ambient temperature over 120°C. This required careful component selection and a lot of power dissipation calculations at the start to ensure that the the natural convection cooling of the component was sufficient to keep the component junction temperature at safe levels. It even included an over temperature shutdown.
As with most industrial scenarios the power supply on both sides was “dirty” with possible spikes and high voltages requiring significant filtering and protection build into the device. The electrical isolation was to 2500V.
It had to provide enough protection and fault detection for easy troubleshooting. The output was current limited and if it was shorted it would have to turn on an LED. Activity on either side had to be easily verifiable by blink of LEDs so a pulse stretcher was used on both sides.
It turned out to work great.
This was a redesign of existing main board with over 300 components of a substation Remote Terminal Unit (RTU).
There were number of new features that had to be implemented requiring complete new layout of the board. I followed number of safety and performance standards as well as the R&D procedures of the ISO9001 certified company.
Since the board was going through a major redesign, I implemented additional changes to reduce the cost of the board by:
• converting all components to SMT type and press fit connectors
• moving all components to one side
• removing 2 internal layers
I used Protel 99SE to update the Schematics and create brand new PCB layout. During the process I kept detail design log and at the end I supervised conformance testing.
This was an interesting project because it had to work on the first try. The purpose of this device was to activate hydraulics on a well drilling head just at the right time. Since the unit is used on a drilling rig where each minute spend at the well testing costs a lot of money it had to work. Along the way there were many unknowns as to how well it will receive the control signals so number of activation methods were conceived.
The solution was in designing two modes. First was a data logging mode that recorded a number of sensors. The tool was lowered, the test signals were sent and the tool was pulled out of the well. The collected data were analyzed within minutes and the tool was configured in the operational mode with settings derived from the logged signals. On the second run down the well it activated.
I designed the sensor interfaces with configurable filters. I prepared the schematics, PCB, Firmware and performed a lot of testing.