In my practice, I place the flyback diodes as close as possible to the relay. A typical 1N diode serves me well in most applications and it saves me from the problem of having to manually create footprints.
This is particularly useful when I repurpose older designs. Have a question about flyback diodes? Contact an expert at Altium Designer. Information for EDA Leaders. Mobile menu. Explore Products. Altium Community. How to Create a Footprint.
More content by Altium Designer. Recent Articles. Should You Use Tight vs. Loose Differential Pair Spacing and Coupling? We get a lot of questions about trace impedance and how to calculate the right trace size to hit a specific impedance in a manufacturable PCB. Just as important as determining an appropriate trace width for a single-ended trace is determination of an appropriate spacing between two traces in a differential pair.
Watch and learn what he will have in store for us. Read Article. Overview of Electrical Stress Test Methods for PCBAs Electrical stress test requirements should be considered as you begin to make a transition to high volume production.
Mark Harris shares his knowledge to streamline processes and maximize efficiencies during product development and production. While that may sound like a far-off dream, this interview with Misha Govshteyn from MacroFab will give you Read Article. Common Mode Choke Selection Noise on power supply lines can be a major headache, causing reliability issues and leading to unexpected system behavior.
Routing Requirements for USB 2. When working with these interfaces, a few simple guidelines can help ensure signal integrity in your board and cut down on EMI. Again 1N will do the job. Additionally, the 1N in single purchase quantities costs the same but has volt rating. Voltage required is the nominal coil voltage, since that is what will be applied.
Give it a factor of 2 for safety. Things aren't always as simple as they seem, though in the case of relays it's highly application dependent. While the diode provides a safe discharge path that preserves your switching transistor and power supply, it can cause a few issues in certain applications.
Relays on closure can form a small weld at the contacts, and by placing the diode there you are essentially preventing the relay from opening with its full force. This can cause the contacts to 'stick' together slightly longer, and overall is bad for the relay. The maximum output current for the popular timer IC is mA, enough to supply a relay coil directly.
Rapid Electronics: relays. Relays are usuallly SPDT or DPDT but they can have many more sets of switch contacts, for example relays with 4 sets of changeover contacts are readily available. For further information about switch contacts and the terms used to describe them please see the page on switches.
The animated picture shows a working relay with its coil and switch contacts. You can see a lever on the left being attracted by magnetism when the coil is switched on. This lever moves the switch contacts. Relay showing coil and switch contacts. The supplier's catalogue or website should show the relay's connections. The coil will usually be obvious and it may be connected either way round. Relay coils produce brief high voltage 'spikes' when they are switched off and this can destroy transistors and ICs in the circuit.
To prevent damage you must connect a protection diode across the relay coil. Most relays are designed for PCB mounting but you can solder wires directly to the pins providing you take care to avoid melting the plastic case of the relay. For example: A 12V supply relay with a coil resistance of passes a current of 30mA.
This is OK for a timer IC maximum output current mA , but it is too much for most ICs and they will require a transistor to amplify the current. Transistors and ICs must be protected from the brief high voltage produced when a relay coil is switched off.
0コメント