Surge Pulse Clamping with Ceramic Capacitors

Started by Klaus Kragelund in sci.electronics.design7 years ago 40 replies

Hi For an application I need to protect the electronics of an RS485 interface from surges (8/20us 1kV pulse) The normal way be to use a...

Hi For an application I need to protect the electronics of an RS485 interface from surges (8/20us 1kV pulse) The normal way be to use a transzorb, in a SMA housing or even a SOT23 device. That is not possible since we have to be able to withstand up to 30V DC on the bus also (that is handled by a special RS485 IC) The problem is that the selected breakdown voltage of the transzorb ...


Discrete custom design of RS485 driver

Started by Klaus Kragelund in sci.electronics.design7 years ago 111 replies

Hi The standard RS485 drivers available has a minimum voltage of 3V and a rarther large drop voltage when loaded with the defined bus load for...

Hi The standard RS485 drivers available has a minimum voltage of 3V and a rarther large drop voltage when loaded with the defined bus load for Modbus of 54ohms, and this causes problems for our design since we have limited power available for driving the bus So, we are thinking about designing our own driver in discrete components, so we can reduce the supply down to 2V and still comply with...


rs485 and RTN

Started by ice in sci.electronics.design8 years ago 21 replies

hi all system: 9600bps rs485 half-duplex with single master and multiple slaves; both master and slave connector have 3 pins (A,B,RTN) cable:...

hi all system: 9600bps rs485 half-duplex with single master and multiple slaves; both master and slave connector have 3 pins (A,B,RTN) cable: about 500mt shielded cable with 2 twisted pairs inside, one pair used for A/B signals other pair used for RTN the system works well questions: 1. the shield of the cable is connected to earth ground (yellow-green wire) at master side only: is t...


Lighning protection

Started by Phil Hobbs in sci.electronics.design5 years ago 35 replies

So I'm looking at lightning protection for the mezzanine units of the cotton spark detection system. I have a copy of Standtler's book,...

So I'm looking at lightning protection for the mezzanine units of the cotton spark detection system. I have a copy of Standtler's book, "Protection of electronic circuits from overvoltage", which is useful but a bit out of date (1989). (He doesn't know about HV depletion MOSFETs or polyfuses, for instance.) It looks as though I can protect the isolated RS485 pair and the power/commo...


Alpha & Omega AOZ1282 buck regulator--experiences?

Started by Phil Hobbs in sci.electronics.design5 years ago 10 replies

Hi, all, I'm doing the back end for that cotton spark detector system. Each integrator box (Pi Zero based) digitizes the output of up to 8...

Hi, all, I'm doing the back end for that cotton spark detector system. Each integrator box (Pi Zero based) digitizes the output of up to 8 sensors and talks via multimaster RS485 or maybe industrial CANbus to a control panel, which sends data to the outside world. (Getting the SCADA security right is the client's job--I bowed out of that bit because I'm not a crypto guy.) I need a 24V...


OPC driver/Software question

Started by Maynard A. Philbrook Jr. in sci.electronics.design6 years ago

I have a device that I made and it has RS485 on it, I put a compatible Modbus firmware in it and wrote a DDE server for the windows HMI...

I have a device that I made and it has RS485 on it, I put a compatible Modbus firmware in it and wrote a DDE server for the windows HMI front end, which seems to work with the custom HMI I wrote and others that are on the market.. There has been chatter that NetDDE is not supported any more and maybe DDE could be short lived, so I was looking into using the OPC as an option which...


complementary cmos levels

Started by Anonymous in sci.electronics.design6 months ago 11 replies

I have a fast 3.3 volt logic level that I'd like to split into inverted and non-inverted copies with minimum time skew. I think that TI...

I have a fast 3.3 volt logic level that I'd like to split into inverted and non-inverted copies with minimum time skew. I think that TI once had a buffer with one input and complementary outputs, but I can't find a reference to that. It's probably slow and obsolete. A TTL to RS485 converter sort of works but would be slow. I could use two separate XOR gates, one as a buffer and the...


Network of MCUs with centralized power supply

Started by pozz in sci.electronics.design4 years ago 18 replies

I'm going to develop a network of 10-30 electronic nodes based on MCU. The distance between them could 100m maximum. There is a single centrale...

I'm going to develop a network of 10-30 electronic nodes based on MCU. The distance between them could 100m maximum. There is a single centrale power supply unit (PSU) that gives power to nodes through a low-voltage 12-18Vdc plus/minus cables. I'm thinking about a two-wires half-duplex RS485. I'll have 4 cables (+/- for power and A/B for signals) and the advantage of differential signal...


Strange high frequency push pull transformer action

Started by mook johnson in sci.electronics.design8 years ago 100 replies

As mentioned before I'm working with a design that has a 10MHz push-pull transmitter to drive a 100 ohm cat6 cable. The cable is terminated...

As mentioned before I'm working with a design that has a 10MHz push-pull transmitter to drive a 100 ohm cat6 cable. The cable is terminated with 100 ohms on both ends and the length is ~200 ft. This is a multi-drop implementation much like RS485 but needed custom drivers due to the environment. The driver is configured as a push pull with 5V on the center tap. The 2n7000 transisto...