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Thanks Bogeyman for pointing out the over-voltage problem (6.6V) if four Alkaline cells are accidentally used, instead of nimh. The device I'm powering operates from 4.8 5.8 volts. Is it ok to use ldos below their drop out? Fixed 5V ldo regulators drop out at 5.2 or higher. But I want to...

I posted two earlier questions about this: thread956-188710 thread240-174281 This seems like a long post, but often when I read through an Engineering Tips Forum thread, your first responses ask for more information about what you are trying to do, why you want to do it, and what you’ve tried...

Dear Keith, Thanks very much for taking the time to search and find a SMD device that will work in place of IRLZ14. For our application, the V drain is 5V, and the continuous load is 25mA with a 0.5 second 135 mA pulse every 2 seconds. I guess the SOT223 case will dissipate that much heat...

Dear Smoking, Thanks for suggesting a more appropriate forum. I was thinking, this is a digital switch. So, switch=relay, I thought: WRONG. But, about physical size of this device, IRLZ14 is TO220 with .13 ohm on-resistance, 60V 10A. It's bigger than a TO92. Don't savy case dimension...

Dear Smoked, Please tell me where to put the post (except up my...). I've tried digikey's excellent search enigne, and Mouser'sd too, but I'm not a very good driver. I found online that Toshiba's SSM3K series might be similar but I didn't discover where to buy them.

Looking for N-channel MOSFET similar to IRLZ14, with low on-resistance (.1-.2 ohm) but smaller, with through hole leads, such as TO92. - >6V @ .3A minimum amps drain

Dear felixc. Thanks for your suggestion. I may try to figure how to use LP2986 and LM3701 if this (below) doesn't work. Couple of days ago, I found a simple low battery cutoff circuit at <http://www.edn.com/archives/1998/091198/19di.htm> It uses a Panasonic MN13812-Q-ND (TO92) voltage...

Thanks Keith, I looked and read, but I still don't get it. I don't have enough electronics savy. Linear Technologies LM1121 series shows some circuit diagrams in their pdf data sheet (1121fc.pdf) showing how to connect pins. but: In the case of adjustable regulator, what value of resistors...

4.8-5.2Vdc, 150mAh device is powered by 4-AA nimh batteries in series. Looking for a simple (few extra components needed) i/c component to regulate voltage in the range of 4.8-5.2Vdc (fully charged, 4-AA nimh can be 6.0Vdc, which might be too much for the device), and, to shutoff device (open...

If you could figure out how to use a 24Vdc 3-way, 2-position solenoid valve for compressed air or inert gasses from 28" Hg vacuum to 125 psig pressure, here's a bargain I noticed a few days ago: <allelectronics.com> CAT# SV-4

Thanks to buzzup and OperaHouse for comments about switching 48 vdc. Based on your comments, I think I'll abandon both the idea of switching 48vdc, and, abandon the idea of dropping 48vdc to 24 vdc to power the sensor. I was hoping to find a small, solid state device that could simply and...

Thanks OpreaHouse, I'll take another look and try to find a SSR (instead of a relay with contacts) to switch the 48 volt load. When the relay closes there is very little load because the blower doesn't begin to turn until about 5 seconds after that. I didn't think about the arc being a...

Dave asked, "Why use 5vdc for the relay instead of 48 or 24 vdc, which is already present?" I thought the 5vdc would be safer, but my judgement about that might be incorrect. I tought like this: Since the onboard sensor relay's contacts are rated 24 vac 3 amp, I thought it was not a good...

Again thanks for spending time to help me. I'm sure the level of my questions shows that I know very little about solid state electronics and I appreciate your patience to explain basic principles to me. My only knowledge about electronics comes from fifty years ago when I was a teenager...

Thanks to everyone who sent me a response. I have learned something valuable from each post. About Zeners in series, should I step the voltage down in steps, like first a 30 volt, followed by a 15 volt, followed by a 5 volt Zener? About Zeners in parallel, do two or three of the same...

To: Dave (dhwilliams), Thanks for the tip. I installed a 24 volt Zener Diode, 5 watt, as you suggested, and it works! It does get hot to the touch, is that ok? Maybe I need a 10 watt Zener? Since the Zener worked for the co2 sensor application, I got a second Zener to drop 48 vdc volts...

Thanks Brian for your quick response. Can you point me toward as website to find a "switching regulator designed for 48V i/p'?

I want to operate a 24 volt device from a 48 volt power supply. Manual says device (a carbon dioxide sensor) will operate at 18-30 vdc (or20-28 Vrms AC) and power consumption is listed at "less than 2 watts @ 24 VAC." Most of the power consumption seems to be from a "heater" that pulses on...