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Sainsmart 7inch TFT LCD monitor

Posted: Wed Feb 26, 2014 1:11 am
by jhbreinholt
Hi,
I recently received a 7 inch TFT LCD display for my Raspberry PI (http://www.sainsmart.com/7-inch-tft-lcd ... 2av-1.html). Unfortunately, the monitor does not seem able to power up. I have tried it with both a 5v and 12v power supply. The control board does not include a LED power indicator, but it does seem to be getting power. Alas, the monitor just seems dead. Does anyone have any ideas? How should the display behave once it is powered up?

Re: Sainsmart 7inch TFT LCD monitor

Posted: Mon Nov 17, 2014 8:37 pm
by Hakugin
I am not sure if you have resolved the issue yet, however I would like to provide some information about the power connector on the SainSmart 7inch TFT that I recently purchased.

The first thing I discovered was the power connector requires positive on the inner post. Second thing is that I was able to reliably power the screen from a 6v 1amp wall adaptor. Since I purchases the screen to be used in a more mobile manner I used a custom made usb cable and was able to successfully power the screen at 5v. Using a tool purchased from Adafruit, "The Charge Doctor" I was able to determine that the screen is only drawing about 500mA of current while on, and drops down to approximately 150-200mA while turned off / sleep. While yes, this would indicate it may be possible to power this from the Raspberry Pi itself, I do not recommend it. I am using a cheap 20,000mAh battery pack I picked up from Amazon to power it and the Pi to prevent possible damage to the Pi.

When you state "The control board does not include a LED power indicator, but it does seem to be getting power. Alas, the monitor just seems dead.", do you see a white light on the left edge of the LCD panel? If the display is getting proper power you should see a white light or glow on the left edge, as this is the screen's backlight. If you do not see this I would suggest checking the cable between the control / driver board and the LCD display. I admit to not doing this myself and believing that my hdmi cable was hosed. Thankfully it turned out to be a loose connection between the display and board. I am also thankful the cable didn't shift the wrong way and short out any pins.

There are plenty of other things that can be checked for issues like this, however I will not get into all of them at this time.

I wish you the best of luck!
- Mike S

Re: Sainsmart 7inch TFT LCD monitor

Posted: Sun Nov 30, 2014 2:29 pm
by sic
Hakugin wrote:I am not sure if you have resolved the issue yet, however I would like to provide some information about the power connector on the SainSmart 7inch TFT that I recently purchased.

The first thing I discovered was the power connector requires positive on the inner post. Second thing is that I was able to reliably power the screen from a 6v 1amp wall adaptor. Since I purchases the screen to be used in a more mobile manner I used a custom made usb cable and was able to successfully power the screen at 5v. Using a tool purchased from Adafruit, "The Charge Doctor" I was able to determine that the screen is only drawing about 500mA of current while on, and drops down to approximately 150-200mA while turned off / sleep. While yes, this would indicate it may be possible to power this from the Raspberry Pi itself, I do not recommend it. I am using a cheap 20,000mAh battery pack I picked up from Amazon to power it and the Pi to prevent possible damage to the Pi.

When you state "The control board does not include a LED power indicator, but it does seem to be getting power. Alas, the monitor just seems dead.", do you see a white light on the left edge of the LCD panel? If the display is getting proper power you should see a white light or glow on the left edge, as this is the screen's backlight. If you do not see this I would suggest checking the cable between the control / driver board and the LCD display. I admit to not doing this myself and believing that my hdmi cable was hosed. Thankfully it turned out to be a loose connection between the display and board. I am also thankful the cable didn't shift the wrong way and short out any pins.

There are plenty of other things that can be checked for issues like this, however I will not get into all of them at this time.

I wish you the best of luck!
- Mike S
Hi, I'm having the same trouble as OP. The 12 V supply I found and first tested has 1200 mA output. Could have that possibly hurt my device. I also couldn't see anything after connecting the power supply as there is no LED indicators. Would connecting my Pi do any help? Thanks.

Re: Sainsmart 7inch TFT LCD monitor

Posted: Mon Dec 08, 2014 7:02 pm
by Hakugin
sic wrote:Hi, I'm having the same trouble as OP. The 12 V supply I found and first tested has 1200 mA output. Could have that possibly hurt my device. I also couldn't see anything after connecting the power supply as there is no LED indicators. Would connecting my Pi do any help? Thanks.
First, my apologies for not responding sooner, I forgot to subscribe to this topic. I do not believe you have damaged the device, I accidentally reversed the polarity the first time I connected a power supply to my LCD. It simply wouldn't turn on at all. The power supply I have is an RCA "universal" that can go as high as 2500mA. I have noticed the device has a power save feature that will turn off the LCD if it does not detect an input signal from any of the 3 inputs. While handy, can be a bit of a pain if your not expecting it.

My recommendations are:
Check the polarity of your power supply.
Check all connectors and make sure cables are snug / locked in place
Test the display using the VGA port and another computer.