Problem Encounter in RS485 Circuit

I had designed a little board to interface USART to RS485 circuit that has two types of connection: one row of the DIP MAX232, or the ISP header for ATmega64-128-1281-2561 family. 

But after few hours of design, I had decided to improve the circuit, by adding automatic capabilities to the T/R signal, instead of using SCK from the ISP header.

After 2 hours of using Google doing some search for circuits that automatically switch T/R signal, I didn't find anything interesting about the problem I have. Only one circuit that uses a simple transistor and few resistors, but that doesn't satisfy me, since I'm not sure if I do switches off the transceiver too early after the last bit had been sent.

I must say that I have a little being lazy guy, since I'm asking for suggestions about that which I think it’s a good idea to ask some help from you guys because I know some of you may encounter same problem as I encounter right now.

My first bet would be to add a capacitor between T/R pins and ground or VCC to add some delay.

Has someone experience with this kind of circuits? Can you share your idea and thoughts about it or someone that can give advice about this?

Bass-Treble Circuit Using Op-Amp 741

Will make this bassamplifier circuit quick and easy. I’m creating a bass-treble circuit using the Op-Amp741. Yes it is simple but don’t under estimate because it is also a powerful bass, treble, volume control is made by General Op-Amp IC LM741.  The maximum voltage that you can input in this powerful bass is 12V, but don’t worry because this circuit also works in 9v and 6 Volts. The circuit has inbuilt pre-amplifier also.

Parts:

IC LM741 x1
T/C 10k,22k,100k   All x1
Triansistor BC148/548   x1
220uF/25V   x2                 
4.7uF/25V  x2
2.2uF/10V x1
10uF/25V x1
Small resistances x12p
Small PF    x5p

Automotive QVGA Time of Flight Sensor

I was searching about the MLX75 automotive sensor that suits to my project, which I planned to make and as well suitable for LED or lase illumination. I planned to use this MLX75 because it has up to 40 MHz sensor modulations and high ambient light robustness.

So after doing long day research about the project that I planned to make, I finally found this site which I think it can help me a lot when it comes to MLX75 because they explain it well and the function of it. I also understand that aside on automotive QVGA Time of Flight sensor of MLX75 it has also response range 800-900 nm.  You can check the details about automotive QVGA Time of Flight sensor, for you to read and understand the function of it as well as the additional features of the MLX75023 sensor.

MLX71120 and MLX71121

Few days ago I was created a circuit diagram using the 315MHz ASK transmitter IC (integrated circuit). This time I would like to study or doing some research about the RF receiver with a use of MLX71120 and MLX71121 RF receiver applications in a balanced loop antenna.

The good news is, after doing plenty of research about RF receiver using MLX71120 and MLX71121 I found this site of Melexis that explain well on the function and where to use this RF receiver. Upon reading and exploring the site I found out that using this MLX71120 and MLX71121 will need exact computation.

Check this RF receiver MLX71120and MLX71121 for your reference.

Low Cost Programming Kit

I heard few students that they are looking some low cost programming kit that they can use to their project. At back of my mind, I said yeah..!! Where can I get this low cost programming kit? After of doing some research and digging some site I found this MLXSPI-01 programming kit, which can support all Melexis kitparts using the SPI.

MLXSPI-01 programming kit features compatibility with nearly any running PC and easy to use software is included. This is specifically designed to program the Melexis family of kit parts using the SPI interface.

This programming kit is also combination of software and hardware, which the hardware need to be connect to the parallel port of a standard pc to operate while the software will generate the timing of all the signals. Check the site to understand more about low cost programming kit.

Local Interconnect Network Overview

Did you know the exact meaning of LIN? I know many of you out there is thinking or searching what is LIN and what is the function of this. LIN is stands for Local Interconnect Network. LIN network is consists have LIN master and LIN slave and one LIN master typically has up to 16 slaves.

Local Interconnect Network group was founded in the late 1990s by the 5 European automakers Volcano Automotive Group and Freescale.  On November of 2002 the first fully version of LIN specification was implemented and published as LIN version 1.3. Version 2.0 of Local Interconnect Network was introduced on September 2003 to expand configuration capabilities and make provisions for significant additional diagnostics features and tool interfaces. For more understanding what is LIN all about check this LIN Video.

Frame Types of LIN:

1. Unconditional Frame. These always carry signals and their identifiers are in the range 0 to 59 (0x00 to 0x3b). All subscribers of the unconditional frame shall receive the frame and make it available to the application (assuming no errors were detected).
2. Event-triggered Frame. The purpose of this is to increase the responsiveness of the LIN cluster without assigning too much of the bus bandwidth to the polling of multiple slave nodes with seldom occurring events. The first data byte of the carried unconditional frame shall be equal to a protected identifier assigned to an event-triggered frame. A slave shall reply with an associated unconditional frame only if its data value has changed. If none of the slave tasks responds to the header the rest of the frame slot is silent and the header is ignored. If more than one slave task responds to the header in the same frame slot a collision will occur, and the master has to resolve the collision by requesting all associated unconditional frames before requesting the event-triggered frame again.
3. Sporadic Frame. This frame is transmitted by the master as required, so a collision cannot occur. The header of a sporadic frame shall only be sent in its associated frame slot when the master task knows that a signal carried in the frame has been updated. The publisher of the sporadic frame shall always provide the response to the header.
4. Diagnostic Frame. These always carry diagnostic or configuration data and they always contain eight data bytes. The identifier is either 60 (0x3C), called master request frame, or 61(0x3D), called slave response frame. Before generating the header of a diagnostic frame, the master task asks its diagnostic module if it shall be sent or if the bus shall be silent. The slave tasks publish and subscribe to the response according to their diagnostic module.
5. User-Defined Frame. These can carry any kind of information. Their identifier is 62 (0x3E). The header of a user-defined frame is always transmitted when a frame slot allocated to the frame is processed
6. Reserved Frame. These shall not be used in a LIN 2.0 cluster. Their identifier is 63 (0x3F).

Source: Wiki

Class AB 30W Amplifier Circuit

I was planning to create a 30w amplifier circuit for my project. 2 days of searching and stumbling around the net, then finally I found a site that answers all my questions and doubt about my project.  My amplifier circuit is a class AB 30w circuit amplifier.

Below is the instruction on how to set up the class AB amplifier circuit for 30 watts.

To set the above amplifier up, set R1 to max and R12 to 0. After doing this successfully, power on the amplifier. Set R1 so that the measured output offset is between 30 and 100mV. Once set, adjust R12 slowly to achieve a quiescent current of around 120mA. Keep checking the quiescent current as the amp heats up as it might change due to voltage drop changes in the output devices caused by heat. The heatsinks should be 0.6K/W or less for two amplifiers.