[SOLVED] 9 V and 5 V UPS + battery monitoring

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dabby21

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hi,

Simple UPS - Electronic Circuits and Diagram-Electronics Projects and Design

the above link is a simple UPS which has an output of 12 V and 5 V. please can you check it out if it can supply 3 Loads (MODULES)
which 1 load has a 5V and 1.5 A minimum input, and 1 module in need of 9V, lastly for the pic micro controller (PIC18f4550). under the uC module , it will supply power to a USB type fountain, LM35 sensor and maybe the battery monitoring IC's.

anyone can help me out how to construct this UPS with battery monitoring?

LM3914 12V Battery Monitor Circuit

the above link is an example of battery monitoring but since the IC is not available here in my place. components is being considered constructing this module. please, any suggestions and guide links so i can check it out its availability. thank you.
 

As it turns out, one of my favorite pasttimes has been to experiment with simulating LED bargraphs.

Here is the design which duplicates (more or less) what the 3914 IC does.



Led's turn on semi-sharply at increments of .6 to .7 V. This layout lights nine led's over a spread of 8 to 14 V. Maximum current through any led is 10 mA.

The zener dissipates around 500 mW maximum. Therefore it should be rated for 1W.

You can substitute whichever zener voltage produces your desired operating range.

You can use fewer stages if desired. You can add additional stages between points A & B. Resistor values can be reduced or increased to change led brightness.
 
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sir thanks for pointing this out..

LED VoltMeter circuit

above link seems to be the same with you're schematic, am i right? i am planning to work on the above link.
 

LED VoltMeter circuit

above link seems to be the same with you're schematic, am i right? i am planning to work on the above link.
Click to expand...

This design uses individual zener diodes for each led. It's okay to go this route. You can customize the volt level where each led turns on.

However the tolerance we usually see for manufacturing zener diodes is 5%. This means you might pick up a nominal 10V zener and it might really turn out to be 9.5V. Or it might be 10.5V.

If you get an out-of-spec zener you'll need to do some work to modify its turn-on voltage.

So if you decide to use more than a few led's, then I recommend my design shown in post #2, on the premise that ordinary silicon diodes:

* are less expensive,
* will create more uniform LED turn-on intervals,
* will cause fewer errors in assembling the components,

as compared to individual zener diodes.
 

sir,

your design at post # 2 can monitor the health battery ? i mean, indicates whether it is full charged, low and over charged?whats the value of each diodes including the zener diode. and how will i attached this circuit to my circuit, i mean +v is how much and whats the meaning of A and B. ill be monitoring a 12V SLA battery..



the above picture will be the SLA battery that i will be using. thanks
 

dabby21, the LM3914 IC is available in the Phillipines from both of the online shops element14 (PHP 89) and RS (PHP 129)
**broken link removed**
**broken link removed**

P.S.: I'm not from your country. I just looked these up from their sites.

---------- Post added at 23:52 ---------- Previous post was at 22:50 ----------

 The battery monitoring has already been discussed, so let's tackle the UPS. The circuit you linked to is not suitable as it is for your purpose and some modifications have to be made.

1) You need 1.5A capacity for the 5V output but the 7805 is rated only for 1A, so it has to be substituted with another IC with a higher current rating. You can use an LM323 or an LM317. The LM317 is more common and cheaper, but it needs a few extra components to set the output to 5V. Whichever IC you use, it has to be mounted on heatsink as it will dissipate several watts.

Still another option for the 5V output is to use the 7805 and add a transistor to increase the current rating. If you want to use that or the LM317 and need help with the extra circuits, just say so.

2) The circuit does not provide a 9V output. This can be done by using a 7809 IC connected exactly as the 7805 is now connected.

3) The LM323 or LM317 output can be used for the uC, etc.

4) All the diodes should be replaced with 1N5408.
 

If you attach a voltage monitor then it is important that your battery always be connected to an automatic charger...

Assuming that's the case, 3 or 4 LED's are sufficient to show battery condition (low, full, overcharged). There's no need to go to the trouble of using a 3914, nor my design with several LED's.

Backtracking to whether your battery is connected to a charger...

An idle battery will eventually get drained by the LED monitor. A single LED will draw 10mA from a battery continually. In 4 days it will draw 1 amp-hour. Then your 5AH battery is down to 80 percent charge. The more LED's, the sooner the battery will drain. This makes it risky to leave an LED monitor attached to a battery, unless it is connected to an automatic charger.
 
@ sir Pjdd,

exactly sir, im working on a DIY UPS for my project design since our system required to back up it for about 30-45 minutes, but since ive got a very minimal knowledge about circuit, all i can count on is the pre defined circuit found on websites or blogs and hope suits for my needs. sir, i really in need of circuit both using 7805 and 7809, also with LM317 and LM323. Regulators 7805 and 7805, i have them both right now,ill check the availability of LM317 and LM323 on our electronics shops right away, so i can further compare the circuits components costs and also availability.

about the LM3914, that was my first choice to come up a battery monitoring but unfortunately its not available in my place, i mean in my province. So was researching on substitute for this. hope you have a good suggestion and please, help me with the circuits.


@sir BradtheRad

sir, about the Battery monitoring, the battery is always connected to an automatic charger, just like a typical UPS.

to both sirs,

thanks for further explanation and for the help regarding my problem.

---------- Post added at 03:50 ---------- Previous post was at 03:34 ----------

@sir Pjdd,

i have checked the IC's LM317 and LM323, they are available sir here in our place.
 

Before giving you a properly modified circuit, let's clarify a few points first.

1. Do you need a 12V output? The 12V output in the link you gave is not regulated. If you don't need 12V (except for charging the battery), it will make the circuit simpler if we just omit a 12V output.

2. What is the current requirement of the 9V line? Can you give at least an approximate figure? If you don't know, can you explain what circuit it will supply?
 
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sir Pjdd,

1. Fortunately, i dont need the 12 V output so surely it will make the circuit simpler, i just need a 9 V output same as 5 V for the uC.

2. For the 9V line, ill supply it to a smoke sensor module, i dont know whats the specific current that it needs but it has a 9V input, ionization sensor is being used on the module. i think it only requires a small amount of current.

for addition requirements,

3. 5 V and a minimum of 1.5 A- for the GSM module.
4. 5V supplied to uC
under uC it will supply a 5 V fountain that will trigger on certain conditions. and a LM35 heat sensor. just like that sir. please include the battery monitoring sir. thanks
 

OK, here's the "UPS" circuit. Remember that the LM323 must be mounted on a good heatsink. Whether the 7809 also needs a heatsink depends on its load current which we don't know. One way to find out is to use it without a heatsink and see how hot it gets. If it heats up quickly and gets very hot, then it needs a heatsink.

The charging current in the original circuit was so small that it would take many days to fully charge your 5Ah battery. I've increased the current but it's still not very high. I don't want to increase it too much because it has no automatic cut-off. Charging it continuously at a high charge rate can shorten battery life. The 22Ω 2W resistor can be substituted with two 47Ω 1W resistors in parallel.



I'll post the battery monitoring circuit later when I've had time to design it. The principle is quite simple, but as with most practical designs, there are some things that need to be worked out carefully to make sure it suits the intended application.
 

a very thanks you sir for this circuit, taking all the components down done, ill make a pcb layout for this one and hopefully a day or two, will be mounted on PCB, please, do on your most comfortable time regarding battery monitoring circuit sir a very big thanks.

by the way sir, i have a noob question, the above circuit will not over charged the battery even it will stay charging on a long period of time? even though our system will be more likely a demo, since it is part of our project proposal. and how long will it fully charge? can it stay for 30-45 minutes sir? cause thats our minimum time span for the battery to back up the system. Still, thanks in advance sir! cheers!
 

dabby21 said:
by the way sir, i have a noob question, the above circuit will not over charged the battery even it will stay charging on a long period of time?
Click to expand...
In theory, it will overcharge the battery if it's continuously connected to the mains for a long time. "long time" here means days and weeks. But the overcharging rate is low so that, in practical terms, it will not do any great harm to the battery.

even though our system will be more likely a demo, since it is part of our project proposal. and how long will it fully charge?
Click to expand...
It's impossible to give a precise charging time because the actual charging current depends on the transformer characteristics and the actual mains voltage. As a rough estimate, it will take about 1-2 days to charge your 5Ah battery from almost empty to full. If the battery was half-full or almost full to start with, it will take less time to reach full charge.

can it stay for 30-45 minutes sir? cause thats our minimum time span for the battery to back up the system.
Click to expand...
If the battery is in good condition and if it has had time to get fully charged, it will power your project for 1.5 to 2 hours.
 
sir,

thank you for a detailed explanation about my questions, estimation will do regarding its battery charging.
As long as we comply the 30-45 minutes requirement to back up the system, its all good sir since it will last for 1.5 to 2 hours if the battery is fully charged.

I have another question sir regarding 7809,can i put a heat sink on it? like on LM323? Since there's a condition that it will in need of heat sink if it goes hot when in used. So we can further avoid any problems on it.
 

Yes, you can provide a heatsink for the 7809 even before testing it to see if it gets hot. It's almost always best to mount any power device on a heatsink. The reason why some are not mounted, if the device does not get too hot without a heatsink, is due to consideration of cost, size and weight.
 
I'll be on it sir.
Sir, was wondering, what IC will you use on your battery monitoring circuit? if you have now in your mind. or a components that you think is hard to find on local electronics shop, so i can check its availability and notify you further sir
 

I'm thinking of basing it on an LM3914. I know you said earlier that it's not available in your local shops and I gave you two online sources in your country in post #6. But international giants like element14 (formerly Farnell) and RS tend to be rather expensive. If you can find them in one of the local shops, they are likely to be much cheaper. The LM3914 is a popular IC and it's likely that some local shops have it. I suggest you ask again.

Anyway, if you cannot find the LM3914, the battery monitor can also be made with quad opamps and comparators like the LM324 or LM339.

---------- Post added at 21:34 ---------- Previous post was at 21:09 ----------

By the way, you may also be interested in a bar graph LED module like this. They look nice and are not expensive. They come in common-anode and common-cathode versions. We need the common-anode version for this project.

 
Copied sir.

I'll ask again the availability of LM3914, LM324 and LM339. for the bar graph LED, how long it is? i mean, how many leds are there inside of it?do they have fixed number of leds?
 

LED bar graphs come in different sizes and different number of LEDs, but the most common type has 10 LEDs per module (which nicely matches the number of outputs from an LM3914) and is about 2 inches long. The small rectangles at the top are individual rectangular LEDs. Different colours are also available.
 
Here's the battery monitoring circuit. The scale is 11V to 13.25V with a resolution of 0.25V. It can be used and adjusted with the battery alone without hooking it up to the UPS unit.



BradtheRad brought up a valid point earlier in post #7 regarding current drain on the battery by the monitor circuit when it's not being charged by the UPS circuit. I've reduced the LED current to about 5mA. With the current drawn by the IC itself, the total drain on the battery is about 10mA.

When everything is connected together, the two regulator ICs also draw standby currents of about 5mA each even if the loads are disconnected. Thus, the total idle current is about 20mA. This drains 10% of the battery's capacity in 24 hours, but only if mains power is off. If it's kept connected to the mains, the idle current is supplied by the mains and does not drain the battery.

Therefore, if the whole circuit is to be disconnected from the mains for extended periods, it will be best to disconnect the battery from the rest of the circuit. A switch between the battery and the rest of the circuit will be a convenient way to do that.
 
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