Hi, I have absolutely no experience in electronics but I had an idea. With the assistance of a local "clever" guy I explained what I wanted to do. I have had my idea in use now for over a year and it is working great. However, the item has many components and I want to know if it could be combined onto one circuit board doing the same functions. I have attached a file to view and I would be grateful to hear the comments. Enjoy and stay safe.

 

I’m seeing a PIR movement sensor, a buzzer, an on/off switch, a battery and a host of voltage converters.

Presumably this system sounds the buzzer when the PIR sensor detects movement, powered by the mains supply or the battery when the mains is not connected? Is the mains supply intended to keep the battery charged?

It does seem overly complicated but it would help if you could clarify the intended functionality in case I’ve got it wrong

 

I’m seeing a PIR movement sensor, a buzzer, an on/off switch, a battery and a host of voltage converters.

Presumably this system sounds the buzzer when the PIR sensor detects movement, powered by the mains supply or the battery when the mains is not connected? Is the mains supply intended to keep the battery charged?

It does seem overly complicated but it would help if you could clarify the intended functionality in case I’ve got it wrong

Hi, you are correct, the mains is to charge the battery when the pir is receiving 12v power from the mains, the battery also has an overcharge/discharge safety module as the battery is connected all the time. The battery is charged by a +-13.2volt source as the PIR is powered by 12volt. That is why I'm using two Buck Modules. We experience loadshedding and the unit was made to allow me to have alarm at home.

 

I get it.
220VAC - 24VDC Step Down converter is used to provide 24V DC from the mains supply
The XL4015 is a DC/DC buck converter to convert 24V DC to 13.2V
The XH-M609 12-36V DC-Output Battery Low Voltage Disconnect Protection Module Board needs 13.2V to charge the battery

Presumably the 12V PIR is also happy at 13.2V so maybe you don't need the second 220VAC - 24VDC Step Down converter, XL4015 buck converter and the XH-M350 Backup Battery Switch Module?

And depending on the PIR output and the buzzer specifications you can probably drive the buzzer directly from the PIR, or worst case through a single resistor and transistor if the PIR doesn't supply enough current.

I'd probably put the switch in the +ve line coming out of the battery.

As far as putting it all into one circuit board, I'd start with a mains power brick to provide 15V DC, and build a custom circuit to charge the battery using a Linear Voltage regulator - only a few components. Are you using a Lead Acid battery? Overall, it probably doesn't use much power so a "trickle charge" is enough to keep the battery topped up.

Hope that helps. Fairly easy to modify what you have to try it.

 

I get it.
220VAC - 24VDC Step Down converter is used to provide 24V DC from the mains supply
The XL4015 is a DC/DC buck converter to convert 24V DC to 13.2V
The XH-M609 12-36V DC-Output Battery Low Voltage Disconnect Protection Module Board needs 13.2V to charge the battery

Presumably the 12V PIR is also happy at 13.2V so maybe you don't need the second 220VAC - 24VDC Step Down converter, XL4015 buck converter and the XH-M350 Backup Battery Switch Module?

And depending on the PIR output and the buzzer specifications you can probably drive the buzzer directly from the PIR, or worst case through a single resistor and transistor if the PIR doesn't supply enough current.

I'd probably put the switch in the +ve line coming out of the battery.

As far as putting it all into one circuit board, I'd start with a mains power brick to provide 15V DC, and build a custom circuit to charge the battery using a Linear Voltage regulator - only a few components. Are you using a Lead Acid battery? Overall, it probably doesn't use much power so a "trickle charge" is enough to keep the battery topped up.

Hope that helps. Fairly easy to modify what you have to try it.

Sorry, I have no clue how to make the changes, It would help if you could send me a sketch on how to try out the changes. I just would like to lessen the amount of components. I am using a lead acid battery. I honestly am working with absolutely no experience. I'm not even a beginner.

 

Okay, I'm reluctant to suggest you experiment with your working circuit because if either you or I get it wrong, you won't have a working circuit any more!

The good thing about 12V lead acid batteries is that, depending on who you ask, they can stay on trickle charge of up to about 13.5V permanently. Someone on this site may explain why this is not advisable but in practice it's okay.

So I'll try to explain how to build a working circuit from scratch. May I ask where you live in case it affects parts you can buy? You mention "loadshedding" which we seldom see in the UK. I'll do a search for suitable components.

 

Okay, I'm reluctant to suggest you experiment with your working circuit because if either you or I get it wrong, you won't have a working circuit any more!

The good thing about 12V lead acid batteries is that, depending on who you ask, they can stay on trickle charge of up to about 13.5V permanently. Someone on this site may explain why this is not advisable but in practice it's okay.

So I'll try to explain how to build a working circuit from scratch. May I ask where you live in case it affects parts you can buy? You mention "loadshedding" which we seldom see in the UK. I'll do a search for suitable components.

Hi, I live in Johannesburg, South Africa. And Thank You so much for willing to assist.

 

Congratulations, you have reinvented the UPS (uninterruptible power supply.) You could buy one already built and eliminate all of your buck converters.

 

I had to laugh, BobTPH is absolutely right, but if you actually want to build something yourself take a look at https://www.instructables.com/Motion-Detector-Alarm-Circuit-Using-PIR-Sensor/ which explains a motion detector alarm circuit nicely.

You'll find a diagram at the bottom of the page. A PIR sensor with 12V battery and a low voltage buzzer connected via a resistor.

First step is to build that and check it works. To this, you can add a 13.2V trickle charger connected to the battery. Most PIR sensors with a nominal 12V supply will work at a lower voltage, typically down to 5V, so if you want to protect the PIR from a slightly higher voltage than 12V you could then put two diodes in series with the battery in the top rail of the diagram.

You can make a trickle charger using a linear voltage regulator like a LM317 - you can buy modules like https://www.ebay.co.uk/itm/295937422105. You can use your mains power to 24V converter but it would be better to use a power supply with a nominal 15V DC output so you lose less power in the LM317 so it doesn't get too hot. Adjust the output voltage of the LM317 to around 13.2V DC and connect across the battery. Test the battery volage with the "charger" connected - it should not exceed 13.2V - in fact 13.0V will suffice. Unless you have very long power outages the lead acid battery will still be powering the circuit even if the voltage drops quite low.

 

I had to laugh, BobTPH is absolutely right, but if you actually want to build something yourself take a look at https://www.instructables.com/Motion-Detector-Alarm-Circuit-Using-PIR-Sensor/ which explains a motion detector alarm circuit nicely.

You'll find a diagram at the bottom of the page. A PIR sensor with 12V battery and a low voltage buzzer connected via a resistor.

First step is to build that and check it works. To this, you can add a 13.2V trickle charger connected to the battery. Most PIR sensors with a nominal 12V supply will work at a lower voltage, typically down to 5V, so if you want to protect the PIR from a slightly higher voltage than 12V you could then put two diodes in series with the battery in the top rail of the diagram. Maybe check this first - I'll post a suggested trickle charge circuit when you are clear about what I've just described.

Thank You so much for the info. I'm going to try your idea. The reason for not just purchasing a UPS, was that I wanted to custom build a solution for my use. I am not a electronics person at all (welder by trade and over 60 years old) so I thought it would be a nice challenge. I knew what I wanted but just did not know how to build it. Once again, Thank You and stay safe until we chat again.

 

Certainly all of those individual functions could be put onto a single circuit board. But there would be massive redundancy at best. A much simpler scheme can be created to provide similar functionality using much less circuitry.

Been there and done that, got the reward. Then got repeated purchase orders fro a very happy customer.

 

Certainly all of those individual functions could be put onto a single circuit board. But there would be massive redundancy at best. A much simpler scheme can be created to provide similar functionality using much less circuitry.

Been there and done that, got the reward. Then got repeated purchase orders fro a very happy customer.

Hi, Jerry-Hat-Trick helped a lot but what you mentioned is exactly what I wanted to do. One of the reasons for building all the functions on one board was, if one of the components failed, I could do the troubleshooting myself and then replace the failed component/s. We experience loadshedding/power outages for long periods of time. When this happens we also run out of water. I have installed a water tank and a 12v water pump which will then supply the bathrooms. This is an emergency backup. The water is used all the time to prevent it from becoming stagnant.

 

In quite a few parts of the world the intermittent water availability has led to most buildings having water storage tanks at an upper level, so that even with a lack of water supply and electrical power, water will be available. So that is a proven way to reduce the impact of the power or water supply. It is neither simple nor cheap, but proven to be reliable.

 

In quite a few parts of the world the intermittent water availability has led to most buildings having water storage tanks at an upper level, so that even with a lack of water supply and electrical power, water will be available. So that is a proven way to reduce the impact of the power or water supply. It is neither simple nor cheap, but proven to be reliable.

Hi, I agree but our property is on level ground and the tank is behind a wall. My concern is that if I raise the tank onto a stand to a height that could give sufficient water pressure, the tank could be "damaged".

 

OK, so that would not be a solution. BUT take a look at Mexico City, and parts of Israel where all have water tanks above.
Another possible option might be a pressurized tank so that the water delivery is powered by air pressure. That is the method used in many places that have wells. The well pump fills a sealed tank and then air pressure provides the delivery push. If the bulk storage tank can't support pressure, a much smaller intermediate tank could serve. A small air compressor could then provide the delivery pressure when needed.

 

OK, so that would not be a solution. BUT take a look at Mexico City, and parts of Israel where all have water tanks above.
Another possible option might be a pressurized tank so that the water delivery is powered by air pressure. That is the method used in many places that have wells. The well pump fills a sealed tank and then air pressure provides the delivery push. If the bulk storage tank can't support pressure, a much smaller intermediate tank could serve. A small air compressor could then provide the delivery pressure when needed.

Hi, That could work. I'll look into that option. Thanks for the idea. Enjoy your day and stay safe.

 

You might even be able to arrange for the smaller tank to fill by gravity flow and not need a pump. Or, if you use a pump, allow the option of gravity fill during power outages. And air pressure from a manual air pump during outages did work on my uncle's farm years ago.

 

You might even be able to arrange for the smaller tank to fill by gravity flow and not need a pump. Or, if you use a pump, allow the option of gravity fill during power outages. And air pressure from a manual air pump during outages did work on my uncle's farm years ago.

Hi, Thanks for the info. But the reason for me wanting to design a circuit on one board is that I use that as a "power pack" for many other items that are powered by 12volt. Such as my cctv cameras, dvr, outside security lights and my router. I have taken modules and placed them in one plastic box, and the outside pir sensors are placed around my home and they are all individually powered. UPS are just too expensive and I thought it would be a nice project for me as I have built about 5 off them. I'm attaching a photo to see what I've done. Just excuse the wiring, it's a mess.

 

OK, and quite a decent packaging arrangement. Certainly a single board combining all of the functions would be less expensive, smaller, and probably more reliable.
I will need to revisit the initial requirements and consider what could be combined while retaining the redundancy needed for adequate performance.

OK, the review completed. So the resulting system would initially be sized to power the motion sensor security system packages. It would need to be scaled up considerably to power a home water supply system.

Starting at the mains connection, there would be simple, standard design power filter to reduce any potentially damaging incoming transients. Following the filter section will be a step down transformer from the 230 volt mains to about 16 volts AC, isolated from the mains. This will feed a bridge rectifier arrangement feeding filter capacitors and providing about 24 volts DC, which will not yet be the regulated voltage.
From the unregulated DC supply will be a switching "buck" regulator circuit that can be adjusted to provide the specified float-charging voltage for the lead-acid battery you have selected. ( The "float" voltage is the voltage that can be constantly applied to a battery with no danger of overcharging. ) The switching regulator must be capable of supplying not only the anticipated battery charging current , but also the required current for the motion sensor and the circuits to supply the detected signal to wherever it is monitored.
This voltage will then supply the rechargeable battery, from which the motion sensor will be powered. An LED indicator will be powered from the unregulated DC power circuit to indicate that mains power is supplied to the package.

All of this functionality can easily reside on a single circuit board, although I suggest that the transformer be mounted off of the circuit board.to allow flexibility in packaging.

A version of this system capable of powering a residential water system will require higher power circuits because pumps require much more power than motion sensors..