Electronic Circuits Projects Diagrams Free - General Electronics Chat

help with vu meter and microphone

fkuk — Fri, 20 Nov 2009 20:07:47 GMT

hi

what im trying to do is make vu meter (lm3916) work with a microphone

but ive noticed that the microphone does not give enough voltage out, so i got a power amplifier (lm386) connected the mic to the amp and then to the vu meter

but all the lights light up

what am i doing wrong is it the amplifier?
if so how do i get it to work

thanks

Elektor Prelude preamp

srcmmr — Fri, 20 Nov 2009 19:57:56 GMT

Hi to everyone,
I am new memeber and i was addressed her from the net.
I found some old copies of Elektor magazine, particulary parts of them, which described a project for an audio preamp called Prelude. Do any of you know something about that? Do any of you ever bulit it?
Any feedback is welcome
Many thanks in advance
srcmmr

Wall climbing..

Electronman — Fri, 20 Nov 2009 17:35:04 GMT

Climb wall car (Remote control)

Want to know how it does work??

Why the voltmeter Shows this?

Electronman — Fri, 20 Nov 2009 17:14:26 GMT

Hi,

Why the voltmeter shows 12V while the above SW is open And was open before( I never closed it!)?

Thanks

Attached Thumbnails

CMOS Inverter 12V INPUT to PIC INPUT

007tiger — Fri, 20 Nov 2009 16:23:49 GMT

I am trying to find a way to replace a reed relay with solid state components.

I have a 12 volt input coming from a remote switch. The system currently turns on a relay that will pull the pic input to ground. The pic input is normally pulled up to 5v.

I think I can use the bottom circuit with a CMOS 4069 inverter to take the 12v input and generate a 5v ttl output. In this circuit the inverter input is pulled low to give me the high output to the PIC. When the switch is pressed the inverter input goes high (+12vdc) and causes the output to go low (<.5vdc) and pull the pic input to ground.

Looking at the data sheet I think I actually have to supply the cmos with 12vdc but this would then give a Vout High of 14.95 volts.

If I keep the CMOS with a 5vdc supply should I use a voltage divider on the input of the CMOS to get the voltage in the 0-5vdc range?

Or is there a better way of doing this? The relay coil adds noise, need a diode for emf and also has a limited mechanical life span, thus I am looking at a more robust solid state design.

Thanks

Attached Thumbnails

RS232 data string generation question

masterice — Fri, 20 Nov 2009 15:45:47 GMT

I have recently been given a batch of (hopefully useful) really nice PCBs and displays.
The display is a 6x20 backlit LCD (Batron BT62005P) and it is driven by an AT89C52 controller which takes serial data from a Maxim MAX233CPP RS232 device.
There's an on board switching converter using an LM2567T device.

I have been told that the RS232 data string for the input takes the form of where ADDR is the line to be written to on the display (0 to 5), and DATA is the 20 ASCII characters to be displayed. Any data not in this format is ignored

I have also been told that the comms are 9600 baud, 8 data, 1 start, 1 stop, no parity

I have tried generating a test string using Hyperterm on the PC but it doesn't really seem cut out for this sort of thing (or I don't know what I'm doing of course).

So does anyone know of any free (emphasis on FREE! :) ) software which can be configured to output this sort of data string from a PC's serial port purely for testing purposes.

The board is also configured for in-board programming of the AT89C52 so also does anyone know of any useful programmer designs or possibly an adaptation for using any of the PIC type of programmers?

Thanks

Slim Haines

Load switch with FET - Is it really that simple?

rprodrigues — Fri, 20 Nov 2009 15:33:00 GMT

Hi guys,

I will use the load switch shown in the picture below to supply current to a 5V / 100mA load.

I made some simulations with PSPICE and the voltage drop across the MOSFET is about 50 mV at 100mA, what is fine for my requeriments.

Am I wrong or the schematic shown is really that simple and enough for my requeriments?

It seems too simple I can not believe!

Thank you :)

Anyone tried this logic analyzer?

Mark_R — Fri, 20 Nov 2009 13:12:07 GMT

Saleae Logic. The Logic Analyzer, Remastered. Now shipping for $149

Watch the video.

The unit and software seems pretty nice, wondering if anyone owns one and how you like it?

Help understanding this circuit?

steve_j83 — Fri, 20 Nov 2009 12:06:59 GMT

Hi all, i would like a little help understanding this circuit

Please correct me if im wrong.

I gather that the tubes when inactive results in a flow to the schmitt triggers which sustain a 5volt output untill there is a completed circuit in the tubes, this creates a voltage drop and this results in a low on the schmitt triggers output.

First question is, it looks to me like the chip is recieving hundereds of volts while the the tubes are inactive. Can the chip handel this?

Secondary keyless entry receiver module

rtm038 — Fri, 20 Nov 2009 08:08:04 GMT

Hello all,
My 06 Ford Expedition has a factory keyless entry system that uses key fobs and a module that is located inside the vehicle. Would it be possible to build a second receiver module that would respond to the "lock" and "unlock" buttons on the factory remote?

Thanks
Ryan

very basic. plz help

D.M. — Fri, 20 Nov 2009 07:23:29 GMT

what do the stars mean on data sheets..

if one goes to page two and looks under any particular specification there may be a star one one of the fields.

http://www.datasheetcatalog.org/data...es/AD202KY.pdf

does that mean it is the same value as written in the previous column? thats all i can think of, i just need to clarify.

thx

Potentiometer Help

chrisdicko — Fri, 20 Nov 2009 07:11:00 GMT

Good Morning,
I have recently fitted a 10kΩ POT to and inverter to control the frequency.

I have added a dial to it for visual reference, ranging from 1 - 12, but when controlling the inverter, the POT doesn't do anything from 1-8 on the dial, but then from 8-12 it changes the frequency from 40Hz to 60Hz (I've set this Hz range on the inverter).

Will changing to a 1kΩ POT allow me to use the full range of the dial?

Both POTs are 1 turn (300 degrees)

Thanks a lot

DC micro motor control

sfink06 — Fri, 20 Nov 2009 02:09:24 GMT

Hi all,
I am looking to design a PCB that can control 10 micro DC motors that run at 3 V and draw 60 mA. Should I be using surface mount H-bridges, and then control the inputs with a PIC? I had trouble finding anything that looked promising in limiting the size of the board. Thanks!

Components Source in Nassau County

mrg1999 — Fri, 20 Nov 2009 01:34:57 GMT

Does anyone have a decent source for electrical components, specifically digital and analog IC's in the Nassau County, NY area?

Usually I buy my components online, but more often than not I find myself shy one or two components for a project that I'd like to pick up right away.

24V battery running 18V

gadgeteer123 — Thu, 19 Nov 2009 22:51:20 GMT

I want to know If i can use a 24V lead acid/deep cycle battery, but only charge it using 20V so i can run a 18V device with it. I cannot find any 18v battery's except ones for drills, and i need a minimum of 10amps of output.