If you ever listen to AM radio, run as fast as you can away from the switching regulators.
We have a bunch of Rush fans and Bible Thumpers that still use AM out here in AZ.Who on earth would listen to crappy AM in the 21st century?
That would be the easy way but where's the challenge in that? Besides, old alternators (mine has a 35 A rating) have poor output at idle so I'd also like to conserve power as much as possible.Use the TO220 version of the 5V regulator, and bolt it to the car... (infinite heatsink)
I still have the original AM radio because 1) I want to keep the original look and 2) basically very few twin shaft radios fit in the dash (see **broken link removed**). This winter, I had the radio refurbished and upgraded to FM with the Aurora FMC-1 FM Tuner. I see that Dimension Engineering has is a 470µF capacitor on the DE-SW033 data sheet. DE told me that this would only be necessary if my device is ripple sensitive. Noise suppression capacitors were common in old cars. Wouldn't a properly-sized capacitor eliminate any noise issues with a switching regulator?If you ever listen to AM radio, run as fast as you can away from the switching regulators.
The old Mopar gauges are thermal devices, which means they have a slow response. I think the RTE applies full 12V power like old mechanical device to allow the gauge to quickly display the sensor reading before slowing its response.The worst part of an original mopar was the bimetal regulator. Why the hell would they duplicate that crappy behavior in that RTE "limiter"? Me-thinks that is like "oxygen free" speaker wire...
AM radio is an amazing invention. Others are just its copies I think. If AM totally disappeared from the earth, many hobbyist and new comers to electronics would feel very sad. Awesome tiny AM detectors are very interesting circuitry to do and to understand and to amaze people (eg crystal radios, matchbox radio, catwhisker detector etc)Who on earth would listen to crappy AM in the 21st century?
35A@14V is 490W. The power wasted in the linear regulator is (14-5)V*0.2A ~= 2W, so the "efficiency" of switcher is a bogus argument...Thanks very much for your quick replies.
That would be the easy way but where's the challenge in that? Besides, old alternators (mine has a 35 A rating) have poor output at idle so I'd also like to conserve power as much as possible.
I still have the original AM radio because 1) I want to keep the original look and 2) basically very few twin shaft radios fit in the dash (see **broken link removed**). This winter, I had the radio refurbished and upgraded to FM with the Aurora FMC-1 FM Tuner. I see that Dimension Engineering has is a 470µF capacitor on the DE-SW033 data sheet. DE told me that this would only be necessary if my device is ripple sensitive. Noise suppression capacitors were common in old cars. Wouldn't a properly-sized capacitor eliminate any noise issues with a switching regulator?
The old Mopar gauges are thermal devices, which means they have a slow response. I think the RTE applies full 12V power like old mechanical device to allow the gauge to quickly display the sensor reading before slowing its response.
Wouldn't the RTE Limiter essentially perform much like the DE-SW050?
It's a bit disappointing that AM music stations are slowly disappearing but there still a few good stations I've been listening to here in southern Ontario (CFZM-AM740 Toronto, WJJL-AM1440 Niagara Falls).
No. You have to understand there are two types of EMI: conducted and radiated. A switcher creates both. A good capacitor may reduce conducted EMI on a given line, but radiated EMI spews like radio waves. The only thing that stops it is either electrostatic shielding or magnetic flux shielding.Wouldn't a properly-sized capacitor eliminate any noise issues with a switching regulator?
Yes, that will help. It will stop electrostatic EMI (like radio waves) but not very effective on magnetic flux that comes off transformers and inductors.As for RFI from a switching regulator, would it be possible to enclose it in a metal box?
Besides, old alternators (mine has a 35 A rating) have poor output at idle so I'd also like to conserve power as much as possible
I see that Dimension Engineering has is a 470µF capacitor on the DE-SW033 data sheet. DE told me that this would only be necessary if my device is ripple sensitive. Noise suppression capacitors were common in old cars. Wouldn't a properly-sized capacitor eliminate any noise issues with a switching regulator?
...I'm pretty sure that the switching regulator will be fine if you wanted to go that way. That is exactly what your alternator regulator is- and the worst type. If push comes to shove you can put the switch mode regulator in a can to screen it.
We have a comedy AM talk radio show that I listen to all the time while driving. All the good talk radio shows left to Satellite radio.Who on earth would listen to crappy AM in the 21st century?
Alternators do use a type switch-mode regulation where the Alternator Voltage Regulator switches the voltage to the field winding (alternator rotor) fully on and then turns it off. Unlike the SMPS Buck Regulator the OP is likely to buy from EBay, the AVR switches on/off 30 to 150 times per second, which causes no detectable RFI at 0.5 to 1.5MHz, partly because the current through the alternator rotor is continuous due to the huge inductance of the rotor winding. The spectrum of the AVRs switching rate is such that you would be receiving the several-thousands harmonic at 1Mhz, which has no detectable energy...
Contrast that to an SMPS that switches at 250KHz. It is really hard to suppress its fourth harmonic to prevent it from clobbering 1MHz..., tin boxes notwithstanding....
Alternators can and do generate some RFI, but it it is wide-band hash due to brush arcing as the brushes ride on the copper slip rings in the rotor. This can be suppressed by mounting a shunt capacitor (with very short leads) right on the alternator (like these). These are effective in suppressing radiated RFI in the 100kHz to several MHz range. This capacitor has nothing to do with filtering alternator ripple, which is an entirely different kettle of fish...
I have a lot of experience installing LORAN and ADF VLF receivers in boats and aircraft. LORAN utilized 100kHz while ADF uses 190kHz to 1.5MHz, and if the alternator filter was missing, reception range would be diminished. Listening to an AM car radio, if the alternator filter is missing, the alternator hash can be heard as a bacon frying sound, especially while tuning weaker AM radio stations.
**broken link removed**Are we going to see a picture of the '65 Barracuda.
Nippondenso externally regulated alternators are a common upgrade but it involves some work. On cars like mine, the full output from the alternator runs through the ammeter with a 12g wire. I have a 90A denso alternator from the junkyard but still have to modify the brackets and wiring.300mA would not bother the alternator. By the way, unless you want to keep the car original, why not fit a modern higher output alternator.
I'm still very new to electronics. What is that lesson?You need to very careful about connecting electrolytic capacitors across the 12V line on a car (auto). The ripple current is the problem. I leaned the lesson the hard way.
I've previously upgraded (back in late 80s) from the single field alternator with mechanical regulator to dual field alternator with electronic regulator (from a 72 Scamp). Are you talking about the mechanical or electronic regulator?That is exactly what your alternator regulator is- and the worst type. If push comes to shove you can put the switch mode regulator in a can to screen it.
Nippondenso externally regulated alternators are a common upgrade but it involves some work. On cars like mine, the full output from the alternator runs through the ammeter with a 12g wire. I have a 90A denso alternator from the junkyard but still have to modify the brackets and wiring.
I'm still very new to electronics. What is that lesson?
I've previously upgraded (back in late 80s) from the single field alternator with mechanical regulator to dual field alternator with electronic regulator (from a 72 Scamp). Are you talking about the mechanical or electronic regulator?
The ugliest EMI comes from the resonant frequency caused by the transformer and inductor's leakage inductance. When the switch snaps off, it rings in the 10MHz - 50 MHz range which is really nasty.The spectrum from a square wave depends on the speed of the rise time and fall time of the edges not on the PRF.
As you say, SMPS' generate all sorts of hash, but my point is that it is quite simple to keep it out of your system by a combination of good layout, screening and filtering.The ugliest EMI comes from the resonant frequency caused by the transformer and inductor's leakage inductance. When the switch snaps off, it rings in the 10MHz - 50 MHz range which is really nasty.
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