Help! Can anyone help me understand a schematic diagram?

[NightHawkRMX]

Hello, I have recently been inspired by a couple of people on YouTube turning laptop screens into battery powered portable displays. I have an old Dell S1709Wc monitor and I am trying to mimic the process for similar results. These tutorials require buying a LCD control board for that specific display since the laptop doesn't have a separate controller for the LCD, however I would like to use the current control board implemented in the monitor. In order to do this I need to know what batteries are needed and how to hook the batteries up to the power supply connection on the control board. Unfortunately, I only have a very basic understanding of electronics and think this project will challenge me and provide a learning opportunity. I have disassembled this monitor and found the following:

+An internal power supply connected to the LCD control board and to the LCD panel directly by 2 dual pin connectors (presumably for the back light). I have since concluded this may be a +5v and -5v arrangement after reading some confusing text from lg, written in bad English here: http://www.datasheetspdf.com/pdf/722659/LG/LM171WX3-TLC2/1

+A controller board (p.n. 715G2904-1-4) connected to a power button and button controls as well as the power supply.

+The LCD itself, a LG LM171WX3-TLC2.

The problem i am facing is knowing what batteries are needed to power the board and LCD, Also how to wire it.I found a schematic diagram for the board here: https://www.manualslib.com/manual/864111/Dell-S1709wc.html?page=33#manual
The connector CN404 is the once that used to be connected to the power supply. I believe pins 1 and 2 are ground while 3 and 4 carry an unknown amount of power. 5 and 6 are for the back light brightness control and possibly something else pertaining to the back light. These most likely tell the power supply how much power to send to the back light, since the controller is not directly connected to the back light and thus cannot regulate the brightness itself. I am hoping to use the main battery pack and a potentiometer to control brightness, replacing pins 5 and 6. I hope the board will work properly without them connected.
So in conclusion, What voltage and amperage do you think is intended to be sent to pins 3 and 4, as well as to the backlight? Also using that info what batteries do you think i should use to get decent battery life while on a budget?

 

[Math Geek]

here is a rather detailed teardown and info for that monitor

http://www.panelook.com/LM171WX3-TLC2_LG%20Display_17.1_LCM_parameter_4731.html

gives input voltages, power draw and so on in the write up. not really sure though how to go about choosing the right battery for it though. obviously it should provide the needed voltage and amps as closely as possible. should be a fun project to learn with as you slowly research each step.

 

[NightHawkRMX]

here is a rather detailed teardown and info for that monitor

http://www.panelook.com/LM171WX3-TLC2_LG%20Display_17.1_LCM_parameter_4731.html

gives input voltages, power draw and so on in the write up. not really sure though how to go about choosing the right battery for it though. obviously it should provide the needed voltage and amps as closely as possible. should be a fun project to learn with as you slowly research each step.

Thanks a lot! there is a lot of useful info on the backlight. does the back light really use 640 v on average? this unfortunately doesn't let me know what power is required for the controller board. Thanks anyhow!

 

[Math Geek]

yes it does but note the current draw is only 9 mA max (.009 amps)!! is why it only uses a total of 10 w typically. remember that V x A = Watts so even a large voltage is not a lot if the current is very low as is this case. in fact the max voltage of 1000-1250 is the start-up voltage and would only be for a quick burst to start the screen. then it drops to that typical 645v at that super low amps.

the control board and built in circuitry handles the voltage regulation and probably uses a capacitor to give that quick start-up burst of voltage. so long as you give that panel the needed 5 volts it should take care of the rest through the followed circuits. i'm guessing al you need is the 5v battery to hook up to it and it should be ok from there. asked my dad about it as he was a navy electrician for 30 years and he verified my thoughts on that. panel takes 5 v so a battery 5v battery with more than the needed amps should do the trick. hooking it up is another thing all together and where the real fun begins for you.

basically check out the power supply for the monitor and it should have the power it provides.that let's you know what the input power needed is. should be 5v output up to a few amps more than likely.

 

[mustyfangers]

Generally you would want a laptop monitor instead of a wall powered monitor due to the fact that the laptop's monitor already runs off on battery power. But powering a wall powered monitor can be done, but it's a little more complex.

For starters, if you look at the power board on page 34 of the manual, you can see on the left side of the page where the wall socket icon is followed by some resistors, capacitors, and inductors. This part is just EMI filtering. Towards the top is a blue diamond looking thing called a "bridge rectifier" which converts the AC voltage into DC voltage. Ideally you would connect the positive side of the battery to Pin 1 and negative to Pin 4. However, you will need 163 VDC at that point for your monitor to operate normally. Carrying around a battery that has 163 V would not be a good idea since voltages that high would probably kill you. Also, you'll see there are red triangles with a "!" inside meaning high voltage danger. There are components that need that high voltage to drive critical circuits. I don't think you will be able to hook up a battery directly to the LCD panel and expect it to work the way you want it to work

The safest alternative and my recommendation would be to use an inverter. An inverter basically takes a low voltage DC, typically 5 or 12 VDC, and converts it to 115 VAC. You would then be able to just plug the monitor's power cord directly into the inverter, and attach your battery to the low voltage side of the inverter. You must also size your inverter correctly to the amount of power the monitor requires. According to the datasheet, the nominal power consumption is 34 Watts. So if you powered the monitor with a 115 VAC wall outlet, the current draw will be around 0.3 Amps (I=P/V). But if you used a 12V battery, the current draw would be about 2.8 Amps assuming the inverter is 100% efficient. In this case, a 75 Watt inverter from amazon would do the trick. https://www.amazon.com/dp/B003Q54V88/ref=psdc_2230642011_t2_B0024S5SZI

From the amazon link, the battery's voltage will need to be 12V. So if the monitor is normally going to consume 2.8 Amps, you can determine how many amp hours you want the battery to be by multiplying 2.8 times the number of hours you want the battery to last. If you want the battery to last one hour, then find a 12V, 3 amp hour battery. If you want the battery to last 4 hours, then find a 12V, 12 amp hour battery, and so forth. Hope this helps.

 

[NightHawkRMX]

Generally you would want a laptop monitor instead of a wall powered monitor due to the fact that the laptop's monitor already runs off on battery power. But powering a wall powered monitor can be done, but it's a little more complex.

For starters, if you look at the power board on page 34 of the manual, you can see on the left side of the page where the wall socket icon is followed by some resistors, capacitors, and inductors. This part is just EMI filtering. Towards the top is a blue diamond looking thing called a "bridge rectifier" which converts the AC voltage into DC voltage. Ideally you would connect the positive side of the battery to Pin 1 and negative to Pin 4. However, you will need 163 VDC at that point for your monitor to operate normally. Carrying around a battery that has 163 V would not be a good idea since voltages that high would probably kill you. Also, you'll see there are red triangles with a "!" inside meaning high voltage danger. There are components that need that high voltage to drive critical circuits. I don't think you will be able to hook up a battery directly to the LCD panel and expect it to work the way you want it to work

The safest alternative and my recommendation would be to use an inverter. An inverter basically takes a low voltage DC, typically 5 or 12 VDC, and converts it to 115 VAC. You would then be able to just plug the monitor's power cord directly into the inverter, and attach your battery to the low voltage side of the inverter. You must also size your inverter correctly to the amount of power the monitor requires. According to the datasheet, the nominal power consumption is 34 Watts. So if you powered the monitor with a 115 VAC wall outlet, the current draw will be around 0.3 Amps (I=P/V). But if you used a 12V battery, the current draw would be about 2.8 Amps assuming the inverter is 100% efficient. In this case, a 75 Watt inverter from amazon would do the trick. https://www.amazon.com/dp/B003Q54V88/ref=psdc_2230642011_t2_B0024S5SZI

From the amazon link, the battery's voltage will need to be 12V. So if the monitor is normally going to consume 2.8 Amps, you can determine how many amp hours you want the battery to be by multiplying 2.8 times the number of hours you want the battery to last. If you want the battery to last one hour, then find a 12V, 3 amp hour battery. If you want the battery to last 4 hours, then find a 12V, 12 amp hour battery, and so forth. Hope this helps.

Thank you for all of your responses. I will use the strategy musty fangers suggested as it seems easy enough. Although math geeks suggestion may work, it is more complex. Originally i wondered if would a 12v 3ah sealed lead acid battery be sufficient, but was concerned about the bulkiness and weight of such a battery. Also, these lead acid batteries didn't include any charger or protection circuit, and thus would not be suitable for this project. Later I found a 12v 3ah lipo battery that would be lighter and more space efficient. This battery had an internal circuit that can prevent over charge, over discharge, and over current. This battery also came with a charger for European looking outlets. I wonder if this would include a U.S. adapter like other retailers. If not, i can use my own one that came with an RC car.This had a cost of $28.89 after shipping from Hong Kong. Battery Link: https://www.tindie.com/products/Power_Modules/12v-3ah-36wh-lipo-batterycharger-lithium-polymer/
Do you think this would be sufficient.