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Re: Very low power flashing LED circuit
On Fri, 3 May 2024 at 11:08, Trevor Gale via <tgale=[email protected]> wrote: Why not use a Zener diode (say 10V) in series with a couple of Schottky diodes to drop 10.4V from the 12V line and connect this via a bias resistor to an NPN transistor with a LED and resistor in its collector load - that LED would illuminate when the 12V line is at or above 11V (11V - (10.4V + 0.6V base bias) will turn on the transistor. If you wish you could run a resistor from this collector to a second NPN transistor such that when the rail drops below 11V the first transistor turns off, raising its collector voltage which will then turn on the second transistor, which has its own LED and resistor as its collector load - indicating that the rail is below 11V... A simple on/off LED would quickly deplete a few AA cells which are expected to last months until such time as the LED goes off.? |
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Re: Very low power flashing LED circuit
Why not use a Zener diode (say 10V) in series with a couple of Schottky diodes to drop 10.4V from the 12V line and connect this via a bias resistor to an NPN transistor with a LED and resistor in its collector load - that LED would illuminate when the 12V line is at or above 11V (11V - (10.4V + 0.6V base bias) will turn on the transistor. If you wish you could run a resistor from this collector to a second NPN transistor such that when the rail drops below 11V the first transistor turns off, raising its collector voltage which will then turn on the second transistor, which has its own LED and resistor as its collector load - indicating that the rail is below 11V...
Thoughts? -- -- F.C. Trevor Gale |
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Re: Very low power flashing LED circuit
¿ªÔÆÌåÓýGentlemen,Thank you for the several, prompt and very helpful suggestions. They are being thoughtfully considered. Regards, Ray, W4BYG On 5/2/2024 16:53, Ray, W4BYG wrote:
I have a need for a LED indicator to tell if the battery voltage on my RV falls below say 11 volts. Can someone lead me to such a circuit? -- "If you want to build a strong house, I'll give you my engineer's number. If you want to build a strong life, I'll introduce you to my carpenter." Lebron and Heather Lackey |
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Re: Very low power flashing LED circuit
I have a need for a LED indicator to tell if the battery voltage on my RV falls below say 11 volts. Can someone lead me to such a circuit?
Just an LED and series resistor will indicate nominal voltage, but would likely continue to indicate below the 11 volt point (not what I'm looking for). A possible embellishment would be to change colors or a different LED, from one state (above 11 VDC), to the other (below 11 VDC). Your attention is appreciated. Ray, W4BYG -- "If you want to build a strong house, I'll give you my engineer's number. If you want to build a strong life, I'll introduce you to my carpenter." Lebron and Heather Lackey -- This email has been checked for viruses by AVG antivirus software. www.avg.com |
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Re: Very low power flashing LED circuit
¿ªÔÆÌåÓý
If you want to get fancy you could have a look at Kevin Darrahs videos on his TrigBoard. believe 1ua.
-=Bryan=-
From: [email protected] <[email protected]> on behalf of swallowp@... via groups.io <swallowp@...>
Sent: May 1, 2024 10:01 AM To: [email protected] <[email protected]> Subject: [Test Equipment Design & Construction] Very low power flashing LED circuit ?
I have been working on the design of a data logger that will run unattended for several months from three AA cells.?
I needed a ¡°Battery Low¡± indicator that would run for a few days on cells nearing depletion, and came across this flashing LED circuit based on an AtTiny85 microprocessor.?
It requires only three components, has a very small footprint and draws about 5¦ÌA when quiescent by making use of the CPU¡¯s sleep capability and watchdog timer.?
The supply can be anywhere between +2.7 and +5.5V.?
As described in the source code at [1] the LED is on for around 25ms in 4 seconds.?
The LED current is set by the resistor and supply voltage, but the value shown results in good visibility of a 3mm LED with a 3V supply.?
The cycle time can be set over a wide range and the output pin can be chosen (in the code) to be either side of the CPU body, making circuit board layout straightforward.?
Note that the code shown in [1] allocates the output to physical pin 3!?
Change int
pinLed = 4;
to int pinLed = 1
to move the output to physical pin 6.
A CMOS 555 offered the next best solution but that had several more components and drew around 300¦ÌA quiescent current which would have drained the battery comparatively quickly.?
There used to be dedicated ICs for flashing LEDs, but these seem to have vanished from the market. PeterS?
G8EZE [1]???????
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Re: Very low power flashing LED circuit
The information from Peter and David was instructive. I am working on a data logger which needs to start logging events that occur before a trigger condition to show what event caused the trigger.
Broadcast transmitters have multiple overload sensors to shut the transmitter down before damage can occur and lock on an indicator to show which section of the transmitter overloaded. The transmitter is then automatically recycled to turn it back on. If three overloads occur in rapid succession the reset is disabled and the transmitter stays off. The overload system then has to be manually cleared before the transmitter can be turned back on. The problem is that an indicator of an overloaded stage is often insufficient for troubleshooting if no visual damage is evident. I am building an Arduino Uno based device which can monitor several transmitter parameters such as voltages and currents, and can timestamp each measurement and add a measurement identifier. Each measurement is then pushed into a queue (a FIFO buffer) in the Arduino RAM and the next measurement is taken. When an overload occurs (the trigger event) the entire queue is dumped into a connected laptop, the queue is cleared, and measurement resumes. That yields a picture of various transmitter parameters leading up to the overload - in effect a parameter measurement time machine. -- Dale H. Cook, Retired AM/FM/TV Chief Engineer, Roanoke/Lynchburg, VA |
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Re: Very low power flashing LED circuit
I don¡¯t know what data you are logging, but a friend logs temperature periodically and transmits that data to a recording device. His power source for the data logger is interesting. He basically charges up a 1 F or so . The device has an antenna that picks up WiFi, mobile phone and other RF coming its way. This is rectified and used to replenish energy into the capacitor. Every half hour or so the temperature is measured , the data send to the logger via WiFi, and it goes back to sleep. Essentially his remote temperature sensor needs no power source at all, just making use of the initial charge put into the super capacitor and the energy harvested from the general RF around.? I realise that the above is different to your suggestion, but I thought an interesting way of measuring data while using minimal power. Of course a solar cell could be used too, but that¡¯s not suitable in the dark. You might want to consider adding a small solar cell to your device - it might be possible to run for years without replacing the battery.?
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Very low power flashing LED circuit
I have been working on the design of a data logger that will run unattended for several months from three AA cells.? I needed a ¡°Battery Low¡± indicator that would run for a few days on cells nearing depletion, and came across this flashing LED circuit based on an AtTiny85 microprocessor.? It requires only three components, has a very small footprint and draws about 5¦ÌA when quiescent by making use of the CPU¡¯s sleep capability and watchdog timer.? The supply can be anywhere between +2.7 and +5.5V.? As described in the source code at [1] the LED is on for around 25ms in 4 seconds.? The LED current is set by the resistor and supply voltage, but the value shown results in good visibility of a 3mm LED with a 3V supply.? The cycle time can be set over a wide range and the output pin can be chosen (in the code) to be either side of the CPU body, making circuit board layout straightforward.? Note that the code shown in [1] allocates the output to physical pin 3!? Change int pinLed = 4; to int pinLed = 1 to move the output to physical pin 6. A CMOS 555 offered the next best solution but that had several more components and drew around 300¦ÌA quiescent current which would have drained the battery comparatively quickly.? There used to be dedicated ICs for flashing LEDs, but these seem to have vanished from the market. PeterS? G8EZE [1]??????? |
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Re: Low frequency LCR meter
¿ªÔÆÌåÓýI second Don¡¯s recommendation. ? My HP4192A has no trouble testing components down to 5Hz with good resolution. It also works well for big Capacitors, too. I needed to measure a 58F (6 series 350F) Maxwell Super Capacitor bank and it did that. ESR was a little tricky, but it worked. ? Your situation is a little different, but it should work. What parameter are you trying to measure Value, ESR, D? ? The Oscillator Voltage range is 5mV to 1.1V RMS. ? Ross ? From: [email protected] <[email protected]> On Behalf Of Don Bitters via groups.io
Sent: Sunday, February 25, 2024 7:54 PM To: [email protected] Subject: Re: [Test Equipment Design & Construction] Low frequency LCR meter ? Another good option would be an HP 4192A LF Impedance Analyzer ? Specifications (Refer to data sheet for complete specifications. )? Frequency Range: 5 Hz to 13 MHz? OSC Level: 5 mV to 1.1 mV? DC Bias: 0 to ¡À 35V? Measurement Range: 1.0000 ? to 1.000M?? Basic Accuracy: 0.15% O ¡¤???????? 5 Hz to 13 MHz variable frequency ¡¤???????? Swept measurement capability ¡¤???????? Gain-phase measurements: amplitude, phase, group delay ¡¤???????? Floating or grounded devices ¡¤???????? Impedance measurement: |Z|, |Y|, Theta, R, X, G, B, L, C, D, Q, Delta, Delta% ¡¤???????? GPIB The 4192A was replaced by the Keysight E5061B ENA Vector Network Analyzer. Lt also goes down to 5Hz. The data sheet can be downloaded from Keysight. ?
? Don Bitters? |
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Re: Low frequency LCR meter
What type of capacitor, what working AC and DC voltages, and what sort of application, would require measurement of the complex impedance at 10 Hz? Are you looking for low ESR or low leakage? How accurate does your resistance measurement need to be? The answers to those questions may point to a viable instrument. Some instrument-grade impedance bridges using an external oscillator are only specified down to 20 Hz, but as you well know instruments are sometimes usable outside of their specified limits.
-- Dale H. Cook, GR/HP/Tek Collector, Roanoke/Lynchburg, VA |
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Re: Low frequency LCR meter
Not an LCR meter, but you can improvise this fixture: Generate 10Hz sine, 10V. From this signal, generate 0.1V with exactly 180 degrees phase. Connect the C under test to the 10V. Connect a variable R and C in series to the 0.1V. Connect their ends together to an AC voltmeter, preferably a selective one to reject possible mains hum. Vary the R and C to get a null. The equivalent series capacitance and resistance of your specimen will be 0.01x and 100x resp. of the known components. This considers your specimen has a dissipation factor 10 times or more worse than your known C, for example if the specimen is a chunk of PCB. If not, you will have to measure the known C's dissipation factor and throw in some math. Daniel Perez LW1ECP El domingo, 25 de febrero de 2024, 22:59:51 ART, Dr. David Kirkby, Kirkby Microwave Ltd <drkirkby@...> escribi¨®: Has anyone any thoughts about how one make an LCR meter that works at low frequencies (below 20 Hz)? I need to measure the complex impedance of a capacitor of a few hundred pF. This presents a pretty high impedance at low frequencies. My HP 4284A goes down to 20 Hz, but a few hundred pF presents an impedance in the M¦¸ range which is higher than the optimal range. But ideally I would like to make a measurement at 10 Hz.? I do have an EG&G DSP based lock in amplifier which could possibly be bought into a setup. Dave |
Dr. David Kirkby, Kirkby Microwave Ltd
Trevor Gale
Ray, W4BYG
Dale H. Cook
Daniel Ricardo Perez