Recent Posts

1

Repair / Re: Need Help Identifying Component with ID '5ACRPT' SOT-26

« Last post by fmashockie on Today at 07:52:44 am »

Wow thank you so much fzabkar!  I did not come across markingcodes.com in my searches.  All the other smd code sites I tried did not come up with this little guy when searching '5AC'.  So I will definitely keep this site in mind for the future.

Thanks again!

2

Beginners / Re: Can a Powerbank be used to start a car?

« Last post by shapirus on Today at 07:52:13 am »

you might even run you battery flat when driving only short distances, which drains the battery more on a motor start than the recharging from driving.

No. The amount of energy spent for starting the motor is tiny. It can be recovered by the alternator in much less than a minute.

The quiescent current, which is consumed by all the devices when the engine isn't running, is a different story, of course. That one is a significant problem when the car is not used frequently enough, especially when it's cold.

3

Beginners / Re: Can a Powerbank be used to start a car?

« Last post by MrAl on Today at 07:51:11 am »

Just a quick reply...

Some cars do not start to generate electrical energy with the alternator as soon as the car starts.  This is very strange but it's probably meant to protect the alternator or something.  It could take as long as 5 seconds as my old Volvo did.  That means you need to supply power for a time longer than the time it takes for the engine to start.  If you don't the engine just shuts right off again.  It's a real pain in the neck.  Some jump starters will not start the car because of this because the engine starts, then the jump starter turns off, then the car stalls.  Then you have to reset the jump starter to try again but it will just do the same thing again because of that delay.

4

Buy/Sell/Wanted / Re: SALE (AU/NZ): Multicomp Pro MP710086 (Owon P4305 rebadge) at element14

« Last post by 5U4GB on Today at 07:46:50 am »

Yep, seeing same.

Now it's a 404, I've reported it via their web feedback page, lets see if/when it gets fixed.

5

General Technical Chat / Bluetooth Beacon

« Last post by Bluetooth Beacon on Today at 07:45:52 am »

The IoT technology has been constantly updated and iterated, and the indoor positioning technology has also undergone earth shaking changes. From room level positioning, decimeter level positioning to high-precision centimeter positioning, the evolution of technology is always unexpected! In the indoor positioning solutions, various positioning technologies appear in turn. Which technology is the most suitable for indoor positioning? Next, from a 360 degree perspective, learn about the Bluetooth indoor positioning technology solutions.
1、 Overview of Bluetooth indoor location technology
The core of the Bluetooth indoor positioning technology is to deploy and install Bluetooth gateway equipment in the environment, passively capture the beacon information transmitted by the Bluetooth beacon on the person/object through the Bluetooth gateway, the Bluetooth gateway will return the collected beacon information to the positioning server through the wired network, and the positioning server will obtain the real-time coordinates of the Bluetooth beacon on the located person/object through positioning settlement based on the known coordinates of the Bluetooth gateway. The
2、 Characteristics of Bluetooth indoor location technology
Compared with Wi-Fi positioning, beacon Bluetooth technology suffers less environmental interference and is battery powered. In addition, Bluetooth has the advantages of low power consumption, long service life, small size of Bluetooth beacon equipment and high penetration rate, so Bluetooth positioning is the most commonly used technology in indoor positioning technology.
In daily life, smart phones and smart speakers support Bluetooth. The popularity and large-scale use of Bluetooth make the Bluetooth chip have a very low price, which is lower than the traditional UWB / RFID scheme. Moreover, large manufacturers such as apple and Tencent’s Bluetooth ibeacon provide positioning technology support.
3、 How does Bluetooth achieve indoor positioning?
The working frequency band of Bluetooth is 2400-2483.5mhz. When Bluetooth initiates a broadcast, in addition to the MAC address of the broadcast itself, the strength of the Bluetooth beacon signal will also be broadcast, that is, RSSI field strength information, which reflects the signal strength of the broadcast packet. According to the RSSI field strength information, the closer the Bluetooth receiving end is to the transmitting end, the stronger the signal strength is; on the contrary, the weaker the signal strength is; Through the transformation of signal strength, the relationship between signal strength and distance transmitter can be found.
By deploying the Bluetooth transmitter, namely the Bluetooth beacon beacon beacon, in the room, the Bluetooth receiver can determine the position of the Bluetooth receiver in the room after receiving the RSSI field strength signal transmitted by the transmitter. This positioning method is called active positioning, and the positioning accuracy is 3-4 meters.
Through reasonable calculation and conversion, the signal strength (RSSI) of Bluetooth beacon can deduce the distance between the beacon and the receiving device.
But the RSSI value of Bluetooth beacon is a reference value. To calculate the distance of the Bluetooth beacon, you must also know the txpower value of the beacon device.
Txpower refers to the RSSI value at a distance of 1m from the Bluetooth beacon. Different equipment, working conditions and site environment will affect the txpower value.
The three variables a, B and C in the formula are empirical values, which need to be accurately adjusted according to the mobile phone system or hardware model. They rely on hardware adjustment, and are difficult to use without data reserve.
4、 Power supply problem of Bluetooth device
It is not necessary to lay cables in the room. Beacon beacons are generally powered by batteries. When the transmission power is 0dB, that is, the broadcast distance is 20 meters, two No. 5 dry batteries supply power, and the battery power can last for 5 to 7 years. Bluetooth ibeacon supports mobile phones. The location and navigation in the room are realized through app or wechat applet. It is usually applicable to shopping malls, parking lots and hospitals.
5、 Bluetooth gateway
In some special environments, such as nursing homes, prisons, detention centers, mobile phone positioning can not meet the needs of personnel management and accurate control. Active beacon Bluetooth positioning is no longer suitable. In order to meet the needs of this kind of environment, a Bluetooth gateway is developed to scan and receive Bluetooth signals. The Bluetooth gateway is used to communicate with the personnel wearing the smart bracelet. The Bluetooth gateway is laid in the room to scan and collect the Bluetooth signals broadcast by the smart bracelet. The function of real-time positioning can also be realized, and the positioning accuracy can also reach 3 to 4 meters.
The Bluetooth Gateway is 3 to 5 meters high in the room. The Bluetooth signal coverage is about 10 meters. Considering the signal attenuation, the Bluetooth gateway is best within 5 meters from the Bluetooth transmission point when the Bluetooth is actually positioned. During positioning, the positioning algorithm must collect at least 3 Bluetooth signals to realize positioning. Compared with Wi-Fi positioning, Bluetooth signals are more stable and positioning accuracy is higher.

Choose The Right Bluetooth Beacon >

6

Other Equipment & Products / Re: Warning to JBC DDE-1C Soldering Station Owners Check Your Firmware! Teardown Vid

« Last post by Horst Zimmermann on Today at 07:44:54 am »

did buy another DDE-2C in the kit with the desoldering tool

i did upgrade my old and the new one to firmware 886887 without any problems

you can clearly see the difference of the screens, the top one is from july 2021 and the bottom from may 2024

the top one (old) looks more washed out and the bottom (new) looks more crisp

7

Test Equipment / Re: Probing at high speeds. Will the 10x probe overload the circuit?

« Last post by tggzzz on Today at 07:43:48 am »

Such probes are really only useful for higher frequency signals e.g. >100Mhz and the lower impedance circuits typically found with high speed signals. There are commercial probes available, known as Z₀ probes, that have a series 450 resistor and have a x10 attenuation when coupled to a scope with a 50 input. Since the cable is terminated at the scope with the cable characteristic impedance it still looks like 50 at the probe end of the cable and doesn't have the excess cable capacitance that is seen with cable terminated by the 1M input of a scope as for a 10M probe. Without the excess capacitance there is no need for compensation.

However such probe present an excessive loading, especially DC loading, on lower frequency and higher impedance circuits so are not generally suitable for most circuit probing needs.

Whether the loading is "excessive" depends entirely on the circuit. Some resistive divider probes have a 5kohm tip resistance.

Z0 resistive divider probes present a more constant loading, which is often more important that the absolute value.

You need to match the probe class to the circuit and measurement; no surprises there!

8

Beginners / Re: Help with modeling CdS cell in LTspice

« Last post by MrAl on Today at 07:42:54 am »

Hi there. I have drawn up the schematic shown below in LTspice (you can download here). What I want to do is simulate light hitting the CdS cell (R12). Can someone please explain to me how I could go about that? Thanks in advance!

Hi,

To do something like this you would usually set it up so that a voltage controls the device.  That way you can change the voltage in order to see what the device does.  The device would be a linear voltage-controlled resistor, but the drive will be nonlinear and depend on a variable we deem to be the Lux input light level.  You could then do an equivalent light level sweep with whatever light levels you wanted to work with.

For this the input light level units would be in Lux.  Depending on where you are going to use it the range of Lux would be different so you'd have to figure out where you want to use it and it may be in more than one location.  You might also want to get a feel for what Lux you might find in different locations like around the house or outdoors.  You could look that up online.  For example, moon lighting at night could be around 1 Lux while at home it may be 100 Lux and in the kitchen 500 Lux.

Next you need the control formula.  The data sheet for your CdS cell will normally give at least two data points, one for low level lighting and another for brighter light.  The low level might be at 1 Lux while the higher level at 100 Lux or more. You can use a simple curve fit method to calculate the formula which would involve an exponential.
For a quick example:
V=90/x^0.8266
This is a behavioral voltage source that provides a voltage that is related to the light input 'x' in Lux. This voltage 'V' is then used to control a linear voltage-controlled resistor with or without a scaling factor.
You can set this up with different scales, so V=90 volts might be R=90k and V=10 volts might be 10k, etc.
The variable x is the Lux input and you can vary that any way you want to and get a feel for what to expect with different lighting levels.
Don't expect this to be perfect though as there are a lot of other variables including part number unit to unit differences.

Note there are also spectral factors that come into play, and also time related factors that delay the change of resistance as the light levels change.  You could add some capacitance for this, but if you only need to look at static operation you don't need that.

9

Repair / Re: Please help, how can I adjust this transistor?

« Last post by Harry_22 on Today at 07:41:05 am »

Probably I found your problem. This is leakage in C18 tantalum.
If I connect 10 kOhm resistor in parallel with C18 the same voltage imbalance is observed.

I attached .CIR file for Microcap below.

10

General Technical Chat / Bluetooth technology

« Last post by Bluetooth Beacon on Today at 07:40:59 am »

With the development of science and technology and the improvement of people’s living standards, people pay more and more attention to the comfort, safety and convenience of their living environment. In recent years, the rise of smart home system meets people’s needs. It effectively establishes a home information network in the home environment, combines various household appliances into an organic whole, carries out centralized or remote intelligent control and management of household appliances, and can exchange information with the outside world.
Due to too many wired communication connections, complex modes, many hidden dangers in the line, and low comprehensiveness and intelligence, wireless communication is the focus of research in various communication industries in recent years. At present, the wireless transmission technologies of smart home system mainly include ZigBee, Wi Fi, LANYA and Z-Wave.
Due to the popularity of Bluetooth, the smart home system controlled by Bluetooth has inherent advantages over other technologies, and its characteristics of low power consumption, fast transmission and long distance add points and color to the application of Bluetooth technology in smart home. With the further development of wireless Bluetooth technology, the continuous expansion of product scale, the increasing maturity of technology and the decline of price, Bluetooth technology is gradually applied to industrial fields and families. Due to the particularity and advantages of wireless Bluetooth communication media, it can be flexibly applied to smart home information network.


Application of Bluetooth in smart home security
The security system can be divided into three parts: defense alarm system, video monitoring system and access control system. Using Bluetooth to control the defense alarm can realize real-time detection, meet the needs of users’ remote monitoring and reduce the false alarm rate.
As a smart home, the video monitoring system includes three main parts – monitoring center, host control and data processing. Using Internet and community network link, the wireless transmission of USB image acquisition is realized through Bluetooth, the image motion is detected, and the short message alarm is realized by GPRS.
The access control system mainly includes two main functions: automatic identification and security management. Through the detection of passage objects, it realizes the security control of access, real-time monitoring and post inspection, and identifies and records the access of personnel. Bluetooth technology can be used to control access control through the password of mobile client.


Application of Bluetooth in smart home appliances
The home appliance system in smart home is generally composed of five parts: smart wear, light control, video and entertainment, smart switch and smart home appliance.
Smart wearable devices refer to independent wearable electronic products such as smart watches and smart phones. The low-power Bluetooth communication technology is used to detect the temperature, humidity, light and other data of the environment, and the wireless transmission technology is used for security alarm. Bluetooth light control system takes mobile phone and PDA as the control end to realize the light switch control, color control and brightness control, and cooperate with the timing function to control the light action.
The audio-visual entertainment system is based on the wireless Bluetooth audio-visual stereo wall. It integrates TV, Internet network, wireless Bluetooth and stereo equipment to realize the wireless connection of audio-visual entertainment. The intelligent switch receiver receives the command transmitted through Bluetooth to realize the light control.
Connect the receiver between intelligent power facilities and lamp tube appliances to replace the traditional manual switching mode and freely switch lamps, light sources, brightness, etc. Smart home appliances include refrigerators, washing machines, microwave ovens, televisions and other large and small home appliances. They are connected with the master station through Bluetooth wireless communication technology and obtain the use information of home appliances through Internet network.
More Info >