2014 has been a very busy year where we were side tracked by custom project for clients. As a result, many of the Rocket Scream products were either out of stock from time to time or didn’t get an update they truly deserve. Of course, the osPID project is one of the unfortunate ones.
It has been ages since we sold the very last unit of the osPID Kit. The kit has went for quite a number of prototype revision since and is finally here for sale! So, what’s new on the latest revision of the osPID Kit?
Better Auto Power Source Selection
On the previous revision, a Schottky diode was used to basically select the power source of the kit (either the USB or the external DC jack). This causes a voltage drop on the 5V voltage rail if only the USB power is available. We have since replaced them with a pair of op-amp comparator and a very low turn-on resistance MOSFET. Now, if you are providing the kit with the power from the USB port only, the 5V voltage rail will be closer to what we expect. This is really an important update because whenever a very bad and low quality USB cable is used (with very high wire resistance), the voltage at the receiving end on the osPID board will be very much less than 5V and add the Schottky diode voltage drop effect, the ATMega328 might go into reset state due to the brown out detect circuitry on the microcontroller.
Better Power Supply Circuitry
We have replaced the previous switching regulator (MCP16301) with a fixed 5V output version from Texas Instruments (TPS62173). No longer we need a pair of precision resistor to set the output voltage of the regulator. This in return provides a more accurate 5V voltage rail and less passive components are used to support the TPS62173.
Micro USB Connector
We have replaced the mini USB connector with micro USB connector. The latter has a higher insertion rate and the chances that you have a micro USB cable lying around nowadays is pretty high due to their vast usage on smart phones.
Transistor Output on the Solid State Relay (SSR) Port
On previous design, a simple current limiting resistor in series with the digital output pin driving the SSR port was used. This however produces a less than 5V output and is unable to drive some SSR that requires at least 5V to work. We have since replaced them with a transistor to drive the SSR.
Louder SMD Buzzer
The previous batch of osPID Kit was assembled by a factory and a miniature through hole buzzer was used. Once the buzzer is being soldered, we won’t be able to remove them as the pins will be covered by the LCD module mounted on the front of the board. Despite checking every single buzzer before sending them for assembly, we have some boards that came back with faulty buzzer. It is nearly impossible to replace the faulty buzzer without removing the LCD module. Using an SMD buzzer allows us to do replacement if a buzzer is faulty. And to be frank, this new SMD buzzer is awesomely loud and there’s zero defect!
Supply Chain Consolidation
On previous revision of the kit, we bought from many component suppliers and these includes major distributors like Digikey, Mouser, Element-14 and some other local suppliers. We have since stream lined our component selection to only use Element-14. This reduces the amount shipment charges, TT charges, import duty and possibility of parts arriving late due to custom inspections. Element-14 have a very supportive sales network here in Malaysia and we were also provided with discounted pricing on our orders despite how small is Rocket Scream.
Back to Rocket Scream Assembly
As we have mentioned above, the last batch osPID Kit was assembled by a factory in Malaysia. The surface mount components assembly quality can be considered good but not great. But, the through hole components assembly workmanship was really below what we have expected. There were too much solder used and there way too much of flux residue being left on the boards. We spent many hours cleaning up the mess. On this new batch of osPID Kit, we are back doing the assembly using our very own reflow oven controller and our impeccable manual soldering techniques! We have started looking at pick and place machine to speed things up and will be getting one some time in the summer. We’ll talk about that on another post!
On behalf of the osPID team (Brett and us), we would like to apologize for the long wait and we hope you guys will use the osPID Kit in an awesome project!
Take care & happy tinkering!