How to Transmit 9 V / 12 V DC over Long Distance ?

 Hey Techies...

    Today we are going to explore how to transmit 9 V / 12 V DC over a  long distance.

    Consider we have a camera installed at one end in a farm which is located 500 meter away from the Power supply, since it is a farm land we cannot simply lay a 240 V ac on ground, since it is hazardous if  the cable damages.

    Also we cannot directly connect the 9 V / 12 V adopter at one end to get the required voltage at another end, because, consider if cable has a resistance of 2 Ohm and Load current  is 1 Amp then V=I*R, 1*2 = 2 V would be dropped across the cable itself. So we will get 2 V less than the actual voltage. So what shall we do in this case ???

    We have to send the voltage which is safe for the humans, So we should step down the voltage to 24 V from 240 V using 24 V adopter at one end and transmit the power over the cable and place a bug converter at the camera end and make it to 9 V /12 V as required.

    This make the system more economic and more safer.

What is Common-mode Voltage Gain ?

• Common-mode voltage gain refers to the amplification given to signals that appear on both inputs relative to the common (typically ground).
• You will recall from a previous discussion that a differential amplifier is designed to amplify the difference between the two voltages applied to its inputs.
• Thus, if both inputs had +5 volts, for instance, with respect to ground, then the difference would be zero. Similarly, the output would be zero. This defines ideal behavior and is a characteristic of an ideal op amp. 
• In a real op amp, common-mode voltages can receive some amplification and thus depart from the desired behavior. Since we are currently defining ideal characteristics you should remember that an ideal op amp has a common-mode voltage gain of zero.
• This means the output is unaffected by voltages that are common to both inputs (i.e., no difference). Figure 1.13 further illustrates the measurement of common-mode voltage gains

Source : Science Direct

WOW ! FRAMs as alternatives to flash memory in embedded designs

 Ferroelectric random access memory (FRAM) is widely known as a non-volatile, stand-alone memory technology that has been a part of the semiconductor industry for more than a decade.

In recent years, integrated circuit manufacturers have been considering FRAM as a strong contender for embedded, non-volatile memory, as an alternative to flash technology. This article discusses key technology attributes of FRAM while exploring specific use cases that demonstrate FRAM’s advantages.

Today there are multiple memory technologies that have the potential to change the landscape of embedded processing. However, none so far have surfaced as a strong contender for replacing flash technology in microcontrollers (MCUs) until FRAM.

What is FRAM?

FRAM is non-volatile memory that has power, endurance and read/write speeds similar to commonly used static RAM (SRAM). Information stored in an FRAM cell corresponds to the state of polarization of a ferroelectric crystal that can hold its contents even after the power source is removed. This is what makes FRAM truly non-volatile. Also, since the energy required to polarize a crystal is relatively low when compared to programming a flash cell, FRAM writes are inherently lower power than flash.

Figure 1. FRAM allows for continuous ultra-low-power data logging and supports more than 150,000 years of continuous data logging (vs. less than 7 minutes with flash)
Here are a few typical applications that use microcontrollers with flash technology today. Let’s look at how leveraging FRAM-based MCUs, rather than flash-based MCUs, bring cost, energy and efficiency optimization.

Data logging:

A typical data logger application such as a temperature data logger can sample at rates anywhere between 1-1,000Hz. Now consider the write time of a single byte in flash memory is approximately 75µs.

In comparison, FRAM technology can be written to at a rate of about one byte every 125 nanoseconds. This is close to 1000 times faster than flash! Now consider the application reaches the end of a flash segment and needs to move to the next one, suddenly there is a 20 millisecond latency while waiting for a segment erase to complete.

The erase latency does not apply to FRAM as it is not required to pre-erase FRAM bytes between writes. A 20 millisecond latency every segment does not seem prohibitive until we calculate how significantly it impacts the maximum write speed. For the purpose of this discussion, consider that the block of memory being written to is 512 bytes in length. A flash memory block can be written 26 times per second including the time taken to complete an erase cycle every time 512 bytes are written. This brings us to a total speed of 13kBps [1].

In comparison, a 512 byte FRAM block can be written to at speeds greater than 8MBps [2]. Not every application requires such high write speeds, but consider if your target application was required to write only 1kB every second, the MCU with flash technology would spend 7% of the time staying active to perform the write. However an FRAM MCU would complete that task in 0.01% of the time allowing the MCU to remain in standby 99.9% of the time, providing significant power savings.

Energy harvesting
Many applications today are focused on using cleaner and greener energy, energy that is derived from natural sources such as sunlight, vibrations, heat or mechanical change. Such applications rely on small bursts of energy that provide power in short time intervals and the MCU is usually down to the wire in terms of how many lines of code can be executed before power is lost. Flash-based applications pay a premium in power, not only because of higher average power while accessing flash, but also because of higher peak power during flash write events.

This peak power is mainly due to the usage of a charge pump and can reach values of up to 7mA, making non-volatile writes virtually taboo in the energy harvesting world [1]. With FRAM there is no charge pump; therefore, no high current writes. The average power when writing to FRAM is the same as when reading from or executing out of FRAM (i.e. there is no penalty for non-volatile writes, making FRAM a truly flexible option for energy harvesting applications .)



Figure 2. All-in-one: FRAM microcontrollers deliver maximum read, write, power and memory benefits

RFID Tags:

Radio frequency identification (RFID) tags are making an appearance in many places: store shelves for displaying prices, name badges at conferences and on industrial automation floors to mark and identify objects on a conveyor belt. Some of these applications require memory writes up to 100 times a day.

Consider a byte of flash memory with a typical endurance of 10K write/erase cycles. To achieve 100K write/erase cycle endurance, the application will have to set aside 10 bytes of flash memory for every one byte of data, meeting the endurance requirements at the cost of high redundancy.

In comparison, an FRAM memory byte can endure 1015 write/erase cycles – 100 billion times more than a flash byte [3]. For applications that require high endurance in the order of millions of write/erase cycles, FRAM’s endurance specification is unmatched by other embedded non-volatile memory technologies available today.

Handheld metering:

Blood glucose metering is one example where loss of power is highly critical. In the case of power failure due to a depleted battery, the meter is required to save a time stamp, store the readings at the time of failure and perhaps even perform a few math functions before shutting down.

Consider a flash-based metering application with a battery that is depleted of charge, the power drop can be approximated to about 300mV in 0.01 seconds. In this time, up to 80K FRAM bytes can be written compared to about 8K bytes in flash. However this is without factoring in the high peak and average current requirements of a flash write, which will drain the battery rapidly, bringing down the backup capability significantly.

Another use case of system backup in power fail events is in energy metering where the energy reading needs to be preserved in non-volatile memory until power is restored. In such cases, the power usage during system backup is critical as backup battery sources are expected to last up to 10 years.

The list of applications where FRAM not only provides differentiation, but may also be the only viable option, is as diverse as is vast. To test drive an FRAM-based MCU check out the MSP430FR57xx series from Texas Instruments Incorporated (TI). Samples can be obtained for free and the MSP-EXP430FR5739 FRAM experimenter’s board is available online for $29.

FRAM can lower system cost, increase system efficiency and reduce complexity while being significantly lower power than flash. If your existing flash-based MCU application has energy, write speed, endurance or power fail backup constraints it may be time to make the switch to FRAM.

References:

https://www.embedded.com/frams-as-alternatives-to-flash-memory-in-embedded-designs/

Low Voltage Vs High Voltage Programming

There are two modes for programming a PIC® Microcontroller, High Voltage (HV) mode, and Low Voltage (LV) mode. The Low-Voltage Programming (LVP) mode allows the PIC Flash MCUs to be programmed using the operating voltage VDD of the device. This offers many advantages to In-Circuit Serial Programming™ (ICSP) designs.

Types of States in Digital Output

 A three-state, or Tri-State, output has three electrical states: One, zero, and "Hi-Z," or "open." The hi-Z state is a high-impedance state in which the output is disconnected, leaving the signal open, to be driven by another device (or to be pulled up or down by a resistor provided to prevent an undefined state).

High-impedance schemes such as three-state are commonly used for a bus, in which several devices can be selected to drive the bus. 

An open-drain or open-collector output pin is driven by a single transistor, which pulls the pin to only one voltage (generally, to ground). When the output device is off, the pin is left floating (open, or hi-z). A common example is an n-channel transistor which pulls the signal to ground when the transistor is on or leaves it open when the transistor is off.

Open-drain refers to such a circuit implemented in FET technologies because the transistor's drain terminal is connected to the output; open-collector means a bipolar transistor's collector is performing the function.

When the transistor is off, the signal can be driven by another device or it can be pulled up or down by a resistor. The resistor prevents an undefined, floating state. (See the related term, hi-z.) 

 A signal line is said to be "floating" if it is not connected to any voltage supply, ground, or ground-referenced signal source.

 Examples:

            An open-drain, high-impedance (hi-z) output when in the off (hi-z) mode

            In microcomputer systems, a data or address bus may, at times, be undriven (floating). This is permissible because control signals indicate when data is valid, so users of the bus know when the signal can be ignored. 

        One form of non-volatile memory device is achieved via floating gates. The gate of a MOSFET has no connection, allowing charge to remain indefinitely. The gate charge is changed using Fowler-Nordheim tunneling or hot-carrier injection. EPROM, EEPROM, and flash memory are examples. 

Source : Maxim

Know the difference : Sensitivity Vs Resolution

 Resolution is the smallest reading difference that is possible in a given measuring instrument. For example, take a scale, also known as ruler, one can see that 1 mm (or 0.1 cm) is the resolution of the measuring scale. For example, I measure the length and width of a book, I can measure it using a scale and say Length of the book is 30.0 cm x 18.4 cm. The resolution of the scale is 0.1 cm as it has 10 equal divisions in 1 cm.

Sensitivity on the other hand is the smallest amount of change in the measured parameter that causes a reading change equivalent to resolution of the equipment. Sensitivity is relevant when measurements are made in units other than the quantity being measured; For example a load cell which converts load to mV, has a sensitivity of mV/V Full Scale i.e. for a 1 Kg load cell with 5V excitation and the output is 3mV, then sensitivity is 3mV for 1V excitation and for 5V excitation it will be 15 mV.

The weighing scale will have a resolution of 1milligram but the component inside i.e., load cell will have a sensitivity of 3mV/V FS.

A sensor has sensitivity while the instrument which displays the final parameter has resolution. Scale for instance has resolution while it does not have sensitivity. Sensitivity is usually attached to sensors or devices which transform from one form to another.

For example, Thermocouple (which converts temperature to millivolts) has sensitivity while a thermometer has resolution.

Finally, Resolution is the smallest increment that can be read from the instrument and sensitivity is the smallest amount applied that can change the reading resolution by its least significant digit.

SMA vs RP-SMA what is the difference ?

When looking for SMA you may find SMA and RP-SMA connectors. What is the difference in these two?

Reverse polarity SMA (RP-SMA or RSMA) is designed to be incompatible with standard SMA connectors to comply with U.S. FCC regulations which seek to prevent consumers from attaching non-standard aerials to wireless devices.

The male RP-SMA connector has the same external housing as a standard male SMA connector except the center male pin is replaced by a receptacle. The female RP-SMA connector has the same housing as a standard female SMA connector however the pin found on a male SMA connector is on the female RP-SMA connector.

Here are some picture examples to help show the difference.

What is RSSI and its acceptable signal strength?

RSSI stands for Received Signal Strength Indicator. It is an estimated measure of power level that an RF client device is receiving from an access point or router. At larger distances, the signal gets weaker and the wireless data rates get slower, leading to a lower overall data throughput. Signal is measured by the receive signal strength indicator (RSSI), which in most cases indicates how well a particular radio can hear the remote connected client radios. Indoor RSSI Set-Up Best Practices Indoor RSSI Maximums For mixed use networks: -75 dB to -80 dB For session based networks: (Such as video conferencing, Wi-Fi calling, inventory management, etc.) -60 dB to -65 dB Recommended Tx Output Power on APs For mixed use networks: (Such as web browsing, accessing email, etc.) 18 dBm to 20 dBm on the 5 GHz radio 11 dBm to 14 dBm on the 2.4 GHz radio For session based networks: 11 dBm to 15 dBm on the 5 GHz radio 11 dBm on the 2.4 GHz radio Channel Width Relation to RSSI Wider channels normally have lower RSSI values. Therefore, smaller channel widths are recommended in all but some special circumstances; when configuring EnGenius APs. Note: Special circumstances are low AP density deployments, such as a small home network. A wider channel setting should only be considered after the RF deployment has been qualified. (40 MHz - 80 MHz and channel widths) Visualize your project's RSSI through the subscription-free network design tool, ezWiFi Planner. Try it now to measure your project's projected coverage. Source : https://helpcenter.engeniustech.com/hc/en-us/articles/234761008-What-is-RSSI-and-its-acceptable-signal-strength-#:~:text=RSSI%20stands%20for%20Received%20Signal,a%20lower%20overall%20data%20throughput.

Why Diode in Arduino Reset Pin ???

                   The thing is that if you have a capacitor with 5V across it, like when the DTR is zero and the reset is pulled up to 5V and you take that end that has a zero and make it 5V, in that instant the end that was 5V now becomes 10V because the charge on the capacitor can not change instantly. This is the basis of of voltage doublers.

              The diode shorts out that 10V to the 5V rail and so quickly discharges the capacitor.