Question for the group..

Started by Dave in sci.electronics.basics9 years ago 27 replies

I have an automatic battery charger which is totally non-functional, apparently not sensing when it is connected to a load, and the first thing...

I have an automatic battery charger which is totally non-functional, apparently not sensing when it is connected to a load, and the first thing I note about it is that it makes prodigious use of the 2N3904 transistor on its main control board. And one of these (2N3904) has an odd characteristic- it measures .676 VDC from emittor to collector, rather than the typical OL that the others m...


Using software to prevent battery problems....

Started by Mr. Man-wai Chang in sci.electronics.basics6 years ago 7 replies

Isn't it silly in the very beginning? :) -- @~@ Remain silent! Drink, Blink, Stretch! Live long and prosper!! / v \ Simplicity is...

Isn't it silly in the very beginning? :) -- @~@ Remain silent! Drink, Blink, Stretch! Live long and prosper!! / v \ Simplicity is Beauty! /( _ )\ May the Force and farces be with you! ^ ^ (x86_64 Ubuntu 9.10) Linux 2.6.39.3 不å??貸! 不詐é¨?! 不援交! 不æ??交! 不æ??å?«! 不è?ªæ®º! è«?è??æ?®ç¶?援 (CSSA): http://www.swd.gov.hk/tc/index/site_pubsvc/page_socsecu/sub_


Diagnose circuit board issue

Started by AK in sci.electronics.basics3 years ago

I am trying to diagnose why the door chime no longer works. The receiving unit sounds the various melodies. The battery...

I am trying to diagnose why the door chime no longer works. The receiving unit sounds the various melodies. The battery voltage is ok. I have thoroughly cleaned the circuit board. The led lights up when the switch is pressed. Any other things to try next? Thanks. https://imgur.com/a/cZH4n5U


help identifying damaged IC

Started by Gareth in sci.electronics.basics5 years ago 2 replies

I'm trying to identify a damaged IC in my son's radio controlled car. It's SO-8 package, I think it's an H Bridge. The part number starts...

I'm trying to identify a damaged IC in my son's radio controlled car. It's SO-8 package, I think it's an H Bridge. The part number starts "CP21" but the last characters are not legible. There is a photo here: http://gareth.awardspace.co.uk Pins 1 & 2 are logic level controls for forwards and backwards. Pins 3 & 4 go to the battery -ve & +ve terminals respectively. Pins 5 & 6 ...


Have 5v regulator need 9 volts

Started by amdx in sci.electronics.basics10 years ago 29 replies

Hi all, Tomorrow I'm working on a power supply to replace a 9v battery. All I have is a *5 volt regulator. I think can use a voltage divider...

Hi all, Tomorrow I'm working on a power supply to replace a 9v battery. All I have is a *5 volt regulator. I think can use a voltage divider on the output, then tie the normally grounded leg to the center of my divider to bring it up to 4 volts. So I have 4 + 5 = 9 volts. If I used 5.1K and 4.3k in series to ground. that would give me 9.1 volts. However there is some current from the ...


Roof co-ax amp supply question

Started by Charlie+ in sci.electronics.basics3 years ago 2 replies

Hi All, I want to test out an in-line aerial amp and have supplied it with 12V battery and circuit for testing as below glummed from the web...

Hi All, I want to test out an in-line aerial amp and have supplied it with 12V battery and circuit for testing as below glummed from the web and spares. I can build things but am no shakes on real theory. It works well but seems a bit noisy (hiss on stereo) but I have it down at the RX end of the co-ax at the moment prior to going up the roof with it, so that might make quite a difference t...


Most efficient way to get 1.5 volts from 3.7 volts or less?

Started by Anonymous in sci.electronics.basics5 years ago 27 replies

I have a digital height gauge that eats batteries. Not a cheap Chinese made one, but a fairly high quality Japanese made one. It uses one SR44...

I have a digital height gauge that eats batteries. Not a cheap Chinese made one, but a fairly high quality Japanese made one. It uses one SR44 battery. For some reason it has started using batteries much faster than it used to. I have tried several different brands of batteries from several different sources and they all seem to last about the same. Because of the bulk of the sliding portion ...


OT: Lead Acid Float Charger

Started by Jim Thompson in sci.electronics.basics6 years ago 54 replies

I drive my pick-em-up truck every few months. So the battery is dead when I go to use it... like today :-( I'm looking for recommendations...

I drive my pick-em-up truck every few months. So the battery is dead when I go to use it... like today :-( I'm looking for recommendations for the _best_ (*) float charger I can buy to just plug the truck into when it's parked. (*) Cost no object. ...Jim Thompson -- | James E.Thompson | mens | | Analo...


Slow-Mo Wired Transmission

Started by Douglas Beeson in sci.electronics.basics8 years ago 19 replies

Hi all, I want to set up a very simple communication system to allow two devices to propagate a digital signal (3.3 or 5V) across a wire that...

Hi all, I want to set up a very simple communication system to allow two devices to propagate a digital signal (3.3 or 5V) across a wire that may be 10 meters long at the most. The speed is very low, only about 20 Hz max. The devices will be battery powered, so I want low power, but there is a little hitch: each of the two devices will be processing an amplified audio signal, single-ended, and ...


OT: cordless screwdriver

Started by Pimpom in sci.electronics.basics9 years ago 15 replies

Is anyone familiar with the cordless screwdriver in the link or a similar one? I'd like to know if using rechargeable 1.2V NiCd or NiMH cells...

Is anyone familiar with the cordless screwdriver in the link or a similar one? I'd like to know if using rechargeable 1.2V NiCd or NiMH cells instead of the specified 1.5V alkalines will result in a severely reduced torque. http://www.ebay.com/itm/Black-Decker-6-Volt-Alkaline-4-AA-Battery-Operated-Cordless-SCREWDRIVER- NEW-/251240800353?pt=Power_Tools&hash=item3a7f1e6061


RE-Tube amp questions

Started by Anonymous in sci.electronics.basics7 years ago 19 replies

Thanks everyone for your answers. I guess I can see some of the reasons why tube amps tend to be low power. I am going to try Jurb's suggestion...

Thanks everyone for your answers. I guess I can see some of the reasons why tube amps tend to be low power. I am going to try Jurb's suggestion and check out Audiokarma. I have found a battery operated headphone tube amp that uses tiny tubes that also looks interesting. What I need to do is find someone local to me that has a tube amp in the 8 to 16 watt range and listen to it. Then hook my P...


Cheapest way to measure this?

Started by Anonymous in sci.electronics.basics5 years ago 8 replies

I have to use a CPAP to sleep well. I'm going camping and will need to bring battery power for the thing. So I would like to measure the power...

I have to use a CPAP to sleep well. I'm going camping and will need to bring battery power for the thing. So I would like to measure the power draw over several nights to see what the highest power draw is. The machine changes the air pressure depending on my particular needs so I can't just plug it in and measure the current draw. I was wondering if perhaps one of those cheap DSOs would be...


Small timer 'project'

Started by Barry Gower in sci.electronics.basics11 years ago 4 replies

I hope someone can help me with this project. I need a very small switch device, no bigger than about 15 mm in diameter and up to say 25 mm...

I hope someone can help me with this project. I need a very small switch device, no bigger than about 15 mm in diameter and up to say 25 mm thick, and powered by a small watch battery. The device would have one main function - when you press the switch, a light (say LED) flashes, at say 1 to 2 sec intervals for around 30 mins, then goes off. That's it. It would also be nice if it had a bat...


OBD II Device

Started by Bob R in sci.electronics.basics7 years ago 1 reply

Does an OBD II device have the capability to read out battery voltage and charge / discharge current? -- -- No signature ---...

Does an OBD II device have the capability to read out battery voltage and charge / discharge current? -- -- No signature --- news://freenews.netfront.net/ - complaints: news@netfront.net ---


White Noise Source

Started by Chiron in sci.electronics.basics10 years ago 72 replies

I need a source of white noise (audio). It doesn't have to be perfect. I seem to recall that you could use a zener diode as a white noise...

I need a source of white noise (audio). It doesn't have to be perfect. I seem to recall that you could use a zener diode as a white noise source. Is this true? Are there any other possibilities? I anticipate using a 9-V battery for my power, and a few transistors to amplify the signal to drive earphones. You may ask, "why the heck would he want to do that?" Good question: http:...


Remote Control

Started by Robert in sci.electronics.basics8 years ago 4 replies

I am looking for a transmitter receiver pair. Transmitter with several control buttons. Size around that of an electronic car key or a little...

I am looking for a transmitter receiver pair. Transmitter with several control buttons. Size around that of an electronic car key or a little larger. Receiver battery operated with open collector or relay outputs. I need to make a home security system that can turn on LED lights and such at outside sheds around 40 feet away. I can find this but the receiver is AC powered. Need batt...


Gimmick needed...

Started by Jim Thompson in sci.electronics.basics10 years ago 22 replies

Gimmick needed... New water softener has a blinking LED when salt level gets low. Of course it's hidden in its own private closet in the...

Gimmick needed... New water softener has a blinking LED when salt level gets low. Of course it's hidden in its own private closet in the garage. Any cute gimmicks out there to "watch" the LED and transmit the info into the house? Power is available in the closet, so battery operation is not a requirement. (I don't want to open the case and void the warranty.) ...


Minimum component efficient voltage regulator

Started by Tim Watts in sci.electronics.basics7 years ago 17 replies

Hi, I'm playing with AVR microcontrollers (I'm more a software/digital person). I'm after a simple efficient on-a-chip inexpensive...

Hi, I'm playing with AVR microcontrollers (I'm more a software/digital person). I'm after a simple efficient on-a-chip inexpensive voltage regulator for the main power rail for a battery powered device. Say 3-6V nominal in, fixed output of somewhere between 3.5-5V. About 0.2A-0.3A max current. Actual voltage is less important than the fact it is stable so I can design to it...


DC offset dual rail battery supply

Started by David White in sci.electronics.basics10 years ago 13 replies

Can someone please have a look at this diagram and advise if it is workable? The object is to output two identical signals, one with a +12V...

Can someone please have a look at this diagram and advise if it is workable? The object is to output two identical signals, one with a +12V shift above DC/GND, and the other a -12V shift. IOW there is a 24V differential between the mid-points of the two waveforms, with respect to each other, centered on the GND reference of the input signal. http://www.4shared.com/photo/9Ixd-Ldp/DC...


Charging lithium ion battery?

Started by Terry Pinnell in sci.electronics.basics7 years ago 3 replies

My ageing smartphone (an HTC Touch Pro 2, running Windows Mobile 6) has suddenly developed the show-stopping fault of refusing to charge any of...

My ageing smartphone (an HTC Touch Pro 2, running Windows Mobile 6) has suddenly developed the show-stopping fault of refusing to charge any of my five batteries. The smartphone itself is almost certainly faulty (I suspect an internal solder joint issue) but before I abandon it I want to try charging the batteries externally. With my DMM I've identified the two (outer) contacts of the four ...