wuemura

Correcting my previous post, the better solution will be the OPA3692 and not OPA3691 http://focus.ti.com/lit/ds/symlink/opa3692.pdf It has a fixed gain of +2. ;D

So i think i will choose the OPA3691: http://focus.ti.com/lit/ds/symlink/opa3691.pdf And like you said, i will use a 75R grounded at the input and a 75R as signal output. One more question, can i make the CD4053 change the internal swich with a CD4017, so i could use a single button to swith the video. I'm thinking in doing a 6x1 switch 6 input and one output.

Ok, thanks.

Hi audioguru, I was looking around but there is so many options like AD8045/AD8074/OPA693 and the list go on. So i just need to know what is the basic requirement before i can choose to use this one or that one. Now i know about the frequency, for video, high frequency is better? Or with what minimum should i work with. This will be much more easy to me to search and choose the right opamp that i need. Thank you.

Hello there! I wanto to build a video component selector to use with my monitor (SyncMaster 730MP), my idea is to use simple components basically CD4053 / NE555 / OPAMP (buffer). So, with opamp should i use or to be more specific what should be my consideration before i select he opamp. I have a bunch of TL072P if i could use it will be nice. Thanks.

Thank you very much Ante! ;D

Sorry to keep you waiting. I could not find the MAX724, only the LT1074CT and LT1074HVCT.

Hello Ante! Don't know, let me check.

Hello Guys! Thank you for the sugestions, but i think is too dangerous to let a kid handle this. So, i installed a small DC/AC converter (12VDC > 120VAC) inside the dashboard and he can use his original PSP AC Adaptor, now he can charge the PSP battery and play, also is much more safe for him and the car because the converter does not get hot and is small. Thank you!

Suggestions?

Man, we dont have a resistor of such low value here, the lowest value that i could find is 1 ohm. The main idea of using two transistors is to let then work as cooler as possible, because this circuit will be in the hand of a 7 years old kid in a closed metal box, even if i install this inside the dashboard it could not get too much hot because, inside the car dashboard is hot already and there is no ventilation.

Man, to see my nefiew cry is heart breaking. :-\ He cryed alot when i said that i won't do it. So here we go again.... I know that switching regulators can do this job well, the problem is not how to build because there is alot of books about it, the realy problem to me is to get my hands on one. Also the LM323, could not find any near by. So i have to do it the old way. Here is my schematic... F1 has no value yet because i have to build first and mesure later, i dont think R1 could get that hot but 1W resistor wil be a safe value to work with, the two TIP42 should get enought current to PSP without getting also too hot. So what you think?

I was afraid of that, so i will have to say a BIG sorry also to this project because with the heatsink, board and transistor the circuit can be bigger than PSP. :o Thank you Audioguru.

Hello again guys :D My nefiew has a PSP, here we go, so he wants to play games in his father car without running out of battery. I know that there are alot of cheap adapters to do this for about less than $10 bucks, but here at Brazil is not so easy to get this stuff with the same price, and game stores that do sell it, is too expensive, including tax over tax the $10 bucks adapter can go easly to about $150, $180, $200... not good. So i thinking in creating a car adapter using the 7805 in parallel. The PSP adapter is 5VDC 2A, when the adapter is used the PSP drain about 1.5A~1.8A, my idea is to use 3 7805 in parallel to provide about 5V/3A, in theory, it should work fine but i dont know how effective this could be for real. I know that there is better way to do this but my goal is to use cheap parts that i have here. Thanks!

Hahahahahahaha. I have a Palm that does this for me, to remember my wife birthday and stuff ;D ;D

Hi Audioguru, Thank you for your help, i will try the 4069 instead. About the 4053, imagine a audio selector with many inputs and every time you turn on your system you enjoy listen to the LP connected at input number 6, i think is more confortable if the device keep it's settings so you don't need to push the select button six times every time you turn it on. To make it "remember" is a good challenge, don't you think? ;D

Hi Audioguru, The push button is connected at J2, yes is what i have, but the output not always alternate it fails many times. The output of 4049 is connected directly to pin 9/10/11 of CD4053. The 555 circuit is just a test for the CD4053... but for my needs it not work because the 4053 resets every time you disconnect the battery. Responding to your question, with R1/R2 you bias the threshold, when the voltage at the threshold is 2/3 the 555 output is put at low level. The output goes to high level when the voltage at the trigger is lower than 1/3, C2/R3 has the same level as the output so when you press the push button (J2 connector) the level changes. C1 defines the startup level (JP1), ground C1 to get low level at the startup or connect C1 to VCC to start with hight level.

Hello guys! I'm using a CD4049 to make the CD4053 switch change, so you can hold the CD4053 switch position when you turn the circuit on, but some times fail and i have to press the switch button a few times and looks like is not precise, schematic bellow. I have made a few other types of circuits to make the CD4053 change position, but none of then can make the CD4053 keep the last position, one of this circuits i used is the 555 and is very simple, it can be used also to test the CD4053. Any ideas on how to make the CD4049 to be more precise? Thanks.

Hey Audioguru, is nice to talk with a guy like you because every mistake i do you say "don't do it, i've done it before" ;D 30 year ago it must be a very interesting year to live in, i was born at 75 so i wonder how it wolud be to enjoy the 60's, Elvis Presley, ABBA shows and so on. Today kids just think in HALO, GTA, MSN... Not that i'm against it, but in my times we enjoy more the time that we had. Some months ago i was thinking to add more features to this like a LCD, PIC, digital controlers and so on, but this surround is good the way it is, like my teacher said to me "keep it simple" ;D Congratulations on your surround, it must be a very interesting pice of hardware!

You are right, here at my mini-lab it works ok but the pioneer has a 5v output and mess up everithing, diode removed :P So, i've played with the levels and make tests in my car, so the R1/2 value now is 62K. Few more samples, you will enjoy this one ;D Download 5 Download 6 Download 7

Cathode at OPAMP pin 3 Anode at R6. I'm still messing around to fine tune this ;D

Don't challenge me, i love a challenge ;D So, circuit is fixed, return C8 to 100uF (bye noise), add a 4148 diode before R6 (OPAMP pin 3), and i play a bit with the levels by changing R1/2 values (still messing around). So check now what i've got ;D DOWNLOAD 3 DOWNLOAD 4

Ok, hold on a minute, dont go any were ;D

Hey, let's get a patent of this before some one do, we've build a echo machine without a echo machine ;D Joking ;D This echo effect is coming from the OPAMP, months before i design the board the way it is now, i've tryed to bias all together the way you said and had the same problem, i get the effect plus this echo overlaping it. My guess is R6, the circuit generate some small echo but depending on the configuration you get more or less of that. That is why i've choose to make two voltage divider for each IC, maybe if we put a diode after R6 to avoid audio return?? (with the cost of 0.7 voltage drop :( ) You are right, it takes about 1.5 seconds to charge, the problem is this 1.5 seconds of noise. I've recorded more two samples, one you will notice the echo and the other one (sorry for the lyrics) you will notice the noise, when he starts to sing is more or less ok, but when the voice decay you hear some discharge like noise. DOWNLOAD 1 DOWNLOAD 2 Do you have more ideas? Thank you.

Hi Audioguru, Changes made, i removed R17/18/32/33 and capacitor C15/17, joined R21/22/26/27/28/29 to R6/C8 point, added 4 more 1M bias resistors at each output and joined then also to R6/C8. Upgrade C8 value from 100uF to 470uF. The "pop" is not gone but is in a level so low that you can't hear it depending on the audio volume, if you can hear it is more like a soft pop, much better that way. But a few problems came with the solution: 1) There is a huge eco overlaping the sound with a few seconds delay. 2) When i turn on the device with effect on looks like the sound is charging someting and is noisy until it get fully charged, since i changed the C8 to a bigger value it must be it. 3) Sound "blow out" a little at high frequency. By the way, i've removed C1/2/9/10, it did not alter nothing at the item 3 above. Thank you.