5V project power supply from AA batteries, L7805ABV and Feetech F5109M servo - schematic verificatio

Question

Hi! I am putting together a project that needs to work in the field for as long as possible. The batteries need to be easily accessible, so I have decided on AA batteries. I have ensured that all components can be powered by 5 volts. I would very much appreciate your review of the design in the...

Mateusz_konstruktor · Answer

. A simpler way to increase the runtime would be to replace the current voltage stabiliser with a low-dropout model. The issue with the battery voltage, on the other hand, is that as it depletes, the voltage is reduced. Here, at least one more cell would have to be added. The whole thing is up for reconsideration in this respect.

Przemcio · Answer

If every mA in the field counts, it might be worthwhile instead of the L7805 to think about a low dropout voltage regulator? Maybe there would be some information on the difference in current consumption and that would be something!

Mabel123 · Answer

I understand, ie:- add one more AA battery in series, there will be six of them there,- replace the L7805ABV stabiliser with an LDO, for example the LDO 5 V LM1117T-5.0.An LDO regulator is basically the same as an LDO stabiliser, just with adjustable output voltage, yes? I need a constant 5 V, also I think I would stay with a regular stabiliser.

viayner · Answer

Hello, LDO means that we have a small voltage drop on the regulator circuit itself, for the LM7805 it is about 2 V, the LM1117 requires about 1 V (minimum difference between input and output). Linear produces for example the LT30xx series where this is in the order of 200-300 mV. Consider maybe an inverter, then the circuit will still work with a considerable voltage drop, well there comes the efficiency of this inverter. It is not a bad idea to separate the power supply for the control system (ESP) and the actuator (servo). Regards

waltersalata · Answer

How much current does the servo draw? How much heat will be given off to the 7805 - count it.

Mabel123 · Answer

I have never used an inverter before. Would it simply be a replacement for a stabiliser? I see something like a step-down converter to 5 volts. It definitely has a higher maximum current draw than a stabiliser. .When the voltage goes below 5 volts, the whole circuit will stop functioning anyway, so there may not be much point in splitting it. As soon as any component gets too low voltage, the whole circuit needs a battery replacement. .Good question. I did not find a resistance for the stabiliser. I also couldn't find the current draw range of the Feetech F5109M servo unfortunately. I would have to physically test the servo under load and possibly select a stabiliser with a higher maximum output current. Assuming or making sure that overall the circuit will not exceed 800 mA, which is the maximum current of the LDO 5 V LM1117T-5.0 stabiliser, then I guess it should not overheat.

Przemcio · Answer

. Mr Fellow - it is usually difficult to find documentation for something that is not there. This servo is most likely FS 5109M because this can be seen even in the photos on the internet at the companies selling it. See Link . I wonder what Uncle Google has in mind when he writes contact current - 1.7A - 6V? As for the L7805 you would perhaps need to see in the documentation what this heat release looks like.

Mabel123 · Answer

Facts. I found that it has a current draw in the range of 6 mA to 1.7 A, so such a simple linear stabiliser is out of the question. Thanks also to the previous responders for pointing out this heat. .Thank you for your attention! I've done a bit of reading and, however, a step-down inverter at 5 V sounds like the ideal solution. It has a high maximum output current, for example 3 A, it doesn't heat up, it has less losses, meaning longer circuit life.

gps79 · Answer

And I would do things differently. I would power the whole thing from 4x1.5V. The nodemcu board has two ams1117 3.3V and 5V regulators in it, each can give 1A of current. I would power the servo directly from the battery and the rest from the existing regulators. Of course, the author hasn't given all the details of the components he will connect, because why should he? As if one were to approach the subject professionally, one would have to put the processor to sleep for downtime and put to sleep or disconnect the power supply from the other components by software.

Przemcio · Answer

Aha! I also thought about this option so as not to pack stabilisers for high current. This sleep is worth considering and BTW - the circuit has an ADC but will it be able to measure own supply voltage before the stabiliser? There would be a Battery Low signal e.g. on a 2mA LED because there are some. .

Mabel123 · Answer

.I'm wondering about the HC-SR501 PIR sensor. It needs to run on 5 volts like the rest of the components and have a range of 5m. I was also wondering about the Seeedstudio 101020793 sensor, but I would have to learn how to connect it bypassing the Grove system overlay.The buzzer is an Iduino ST1143, for example. .As far as I have read, the NodeMCU ESP-32S feeds 3.3 volts from its pins, meaning it could not power the sensor and buzzer, which need 5 volts. The sensor is supposed to work all the time, so putting it to sleep is unnecessary. Likewise with the processor. Unless I misunderstand the concept of putting it to sleep.Putting the buzzer and servo to sleep might make sense. I understand that this would involve connecting their VINs via a transistor controlled by the controller, yes? Since a stationary servo and a non-writing buzzer don't use much power, it would have a noticeable effect on current consumption? .I was thinking of using a LM2596 converter . How do you get the information that the voltage before the inverter is below some level, in this case 5 volts - the minimum drop across the inverter?

gps79 · Answer

The PIR draws a relatively large amount of current. The whole thing probably won't be suitable for battery power (the operating time will come out to about 1 day on a set of alkaline batteries), so there's nothing to pin down on optimisation. I suggest you list what components the whole system will be made of, determine their power consumption and do an energy balance. From this, the energy requirements will come out. Without a picture of the whole, you will have to change the concept every now and then as you add requirements as to the shape of the device.

Mabel123 · Answer

.Components I would like to use along with the power consumption found:- NodeMCU ESP-32S - approximately 80 mA- Feetech FS5109M servo - 6 mA to 1.7 A- PIR sensor HC-SR501 - approx. 0.6 mA- Iduino ST1143 buzzer - approx. 30 mAThe ESP-32S NodeMCU will not use WiFi or Bluetooth, but will work all the time. I anticipate that the servo will run at full power consumption for about 30 s per day. The signal received from the sensor will be every 5 s. The buzzer will also only run a few seconds per day. All in all, as far as I can count it correctly, it comes out to about 175 mA.Go ahead and suggest replacements if I have chosen some grandfathered components. Everything must run on 5 V, the servo must have a torque of about 10 kg-cm, the motion sensor must see a minimum of 5 m. NodeMCU ESP-32S I already have in stock.

Przemcio · Answer

A small correction regarding the current consumption of the HC-SR501 motion detector - 50uA is the current 50uA is the resting current and a little more during operation. The device is supposed to operate in a closed room as I understand it. At the design stage, no offence, you have to fiddle around a bit with everything so that everything is clear from A to Z. You can see for yourself that not everything everything is described at the time of purchase and you have to do a bit of research so that there are no unpleasant surprises or other disappointments.

Mabel123 · Answer

Ah, now I see, PIR sensor HC-SR501 - about 60 mA during operation. So all in all about 235 mA.The device is intended to operate outdoors.Please feel free to attach . Edited: An AA battery is approximately 2500 mAh. Six of these will be 15000 mAh and 9 volts. The 5 volt inverter, if I understand it correctly, will stop working when the voltage from the battery goes down to 5 volts. How do you calculate when this will happen? From the ratio I came up with around 27 h at 250 mA draw.

gps79 · Answer

At different voltages, mA (or mAh) are not comparable. The balance must be done in units of energy (voltage x current), e.g. watt-hours [Wh]. Devices consume 5V * 235mA = 1.175W. Assume that the voltage converter will have a loss of 20%, so the power drawn from the battery will be 1.175W + 20% = 1.41W. You build a 9V battery (6 2500mAh cells connected in series). The battery is 2.5Ah at 9V, so 22.5Wh. A 22.5Wh battery charged at 1.41W will give out energy for 22.5Wh / 1.41W = 16h. I suggest changing to a sensibly sized battery.

Przemcio · Answer

. Do not provoke ! The ESP-32S alone draws up to 260mA depending on the mode of operation. If this is to work outdoors then think about an airtight housing with a transparent cover for the PIR. cover for the PIR. But this may limit its range. Modules for Arduino, ESP and the like are unlikely to be intended for use in harsher than room conditions unless the manufacturer has stipulated otherwise. Well, and there will be some testing and calculations but this is how the device is made! Rather, it will continue to be 2500mA and 9V. But on standby milliamps will be needed as long as the PIR is not too sensitive to mosquitoes. Colleague gps79 rightly suggests a battery. And if it's going to work outside then maybe some recharging from micro solar panels?

Mabel123 · Answer

Super! Thank you very much for explaining how to calculate this energy balance.As a first iteration, I will prepare the device on batteries. 16 h will allow to estimate if the construction makes sense at all. If everything goes bold, I think I'll be tempted to go for that battery, maybe even solar panels. The battery pack is a big enough expense that I'd like to test the minimum version first. Repowering from battery to battery shouldn't be a problem, since it'll go through the inverter anyway.

Mateusz_konstruktor · Answer

Here, there is no need to build according to one's own imagination and then find organoleptic failures that are easy to predict. Let us start with the question of servo current consumption. What is the maximum current, particularly at start-up? Here, the phenomenon of a momentary heavy load on the battery and a consequent drop in the supply voltage is to be expected. The end result can be various hang-ups and restarts, and what may be one of the biggest challenges of this project.

LEDówki · Answer

One battery is not enough. You will need a battery of batteries. Of course, nobody wants to read the basics of how batteries are connected and what the characteristics of these connections are. Too much knowledge gives you a headache... You have been given on a tray how much energy you will need to operate the device. It remains to select the capacity and number of batteries to provide this energy. The type of battery is probably new-fashioned - lithium-ion, which requires the addition of safety devices, as batteries are expensive, capricious and explosive. If it is to be non-explosive, they can be NiMH with a capacity of 3Ah. You need a lot of them to have a voltage higher than 5V. Plus an inverter to reduce the voltage. LM7805 convenient but hopelessly inefficient will shorten the circuit. A solar battery charger is fine, but you need to embrace battery power for the circuit first. The author will not learn everything in an instant. The author wants to experiment, which is not necessary when there are promoters overseeing the design of the device. This allows you to learn from other people's mistakes and save resources for experimentation.

JacekCz · Answer

. Because a stabiliser has no resistance (understood strictly according to theory as lionic) - it would not be a stabiliser. The loss in heat is always the same: Delta U * I. Buddy, this is a primer No offence, but before there is schematic verification there is a lot of prior homework with amps, volts etc. Yes, in a colleague this is exactly the kind of project: grab a soldering iron and theory is for wimps. And knowledge: e.g. you can see the concept of the LDO was not very familiar.

LEDówki · Answer

>>21576530 . The inverter will stop working sooner. The minimum voltage difference between input and output is described in the inverter documentation. The LM7805 requires a 3 V voltage difference between input and output. A 9V battery consists of 6 cells. The minimum cell voltage is 1V at some current. Maybe 0.9 V. 6x0.9 V = 5.4 V - at this voltage the battery will be exhausted. To get the voltage at the input of the 7805 to at least 8V you need to assemble a battery with at least 8 primary 1.5V cells. After discharging them to 1V, there will be just 8V at the input of the stabiliser. This is assuming that the cells are identical and will have the same voltages all the time. However, this will not be the case. Inverters have a lower permissible voltage between input and output, and this is also to be checked in their documentation. By increasing the voltage you increase the Wh, so such a battery will last longer. The inverter has better efficiency than the LM7805. The higher the current draw, the faster the voltage drops across the internal resistance of the electrochemical cell (primary or secondary i.e. battery). The power loss in an element P=U*I, is a basic formula from grade 7 in primary school. Transformations with resistance and current or voltage were not until secondary school (vocational/technical school).

5V project power supply from AA batteries, L7805ABV and Feetech F5109M servo - schematic verificatio

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