![]() A Which HuntĪ product introduced without adequate EMC testing can cause a “which hunt” when customers complain. ![]() In either case, the solution is adjusting the frequency of the PWM signal in software to get outside of the problem area. Alternatively, radiated EMI can occur as well. “If you run them at the right frequency, sometimes you can have a conducted path coming back through the wiring and that can affect some other device,” says Bogden. The PWM technique tends to generate both conducted and radiated waveforms. For example, pulse width modulation (PWM) control for a motor or solenoid. Changing the timing loop slightly is an easily implemented fix.Ĭertain control techniques are known to produce problems. “This is very rare, but I have run into it in the past,” he quickly adds. “You may find out that you are generating a periodic frequency that happens to create a problem someplace else,” says Bogden. Software executing periodic timing loops can create problems, too. “First of all, you have to select the microprocessor crystal frequency so that it doesn’t lay on top of other radio frequency bands,” says Bogden. ![]() Microprocessor clock frequencies and software loops can pose unique problems that are normally easy to detect. A software routine that monitors the switch bounce and provides adequate settling time before making a reading is a common solution. ![]() With a switch, switch bounce and arcing can occur. From an immunity point of view, the software is not impacted, but the right software can reduce EMI. Software is an important consideration for some EMC problems. Worst case, shielded wiring may be required, but twisted pairs or just keeping certain wires away from each other may be the solution to a direct influence of EMC. “You can find a component that works fine in its own component testing and then you hook up the antennas and the conduction to it and all of a sudden it has a problem,” says Bogden. As a result, EMC testing done at a component level does not provide a complete picture. Wiring is part of the consideration for both conducted and radiated emissions. Bogden points out that there are five different EMC domains: radiated immunity, radiated emissions, conducted immunity, conducted emissions and electrostatic discharge (ESD). Currently owner and chief engineer at Robotronics SP, a consulting firm specializing in the design of embedded electronic products, he still has to deal with EMC. Understanding the Impact of EMIĭennis Bogden, retired director of Powertrain Electronics Engineering at General Motors, has had extensive experience in dealing with critical vehicle electronics systems. It’s been there long before the first digital electronics and the first microprocessors were introduced to vehicles in the 1970s. Since EMC impacts every vehicle electronic system, Auto Electronics contacted some knowledgeable experts to shed a little light on EMI/EMC. This is a topic that many people know little about except those automotive experts that deal with it on a daily basis. The recent Toyota recall has brought a lot of attention to electromagnetic compatibility (EMC) and electromagnetic interference (EMI). This article is part of the TechXchange: Delving into EMI, EMC and Noise
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |