Problem with VQE-24

I have problem with this number 'lcd'

The LEDs are controlled by GND and A1 and A2 are PLUS. There are 18 pins which 2 are + ,16 -, but my arduino has only 3 GNDs. Is there a possibility to make some digital pins to GND or something like this, or I have to make this work with transistors ???

Thanks in advance!

Just connect all the grounds together and connect to one of the Arduino grounds. All the Ground pins on the Arduino are connected together.

But the lights are working with - not + .If i had 16 + this was no problem, but to control them I need 16 -

There must be more to the story than you are revealing. Do you have a link to a site where this device is described, that has more detail than this picture?

I don't see anything in this picture to back up your claim of 16 - pins. If the device really does require a negative voltage, you won't be able to drive it without additional hardware.

Well this device is maybe 15 years old/maybe more/ and its a huge that i found even that datasheet at the internet. Yes it require negative voltage and i think to make this run I need 16 transistors for negative part ...

There's a clearer pin out here:üter-Bastelei/DDR-Halbleiter/vqe21.gif

As its a common-anode display you need to drive each anode with a transistor - so 2 Arduino pins for them. Common-up the segments in pairs: A1 and A2, B1 and B2 etc. These are then driven via current-limiting resistor from 7 or 8 other pins (depending on whether you need the decimal points). Something like 150 ohm or more will do and keep the current to safe level for the Arduino to drive.

For the anode-driving transistors you can use PNP in common emitter configuration or NPN in emitter-follower configuration. Or logic-level p-channel FETs, but bipolar transistors are probably cheaper.

The sketch then drives each digit in turn by setting that anode on, and setting the segments to the desired state (LOW means on for cathodes).

The sense of driving the anode depends on whether PNP common-emitter (LOW means on) or NPN emitter-follower (HIGH means on).

My guess is that the thing works like this:

Two 7 segment displays, each with an independent common anode or cathode pinout. In other words, it's like two independent single digits, each with a nine pin scheme, just wedged into one casing. They're not multiplexed through the segments. Yours, the VQE24, has what looks like common anode (on each digit, independently) on pins 4 and 5 respectively. The data sheet is needlessly confusing by referring to the seven segments as A,B,C,D,E,F,G (as usual) and then H for the DP. Then it refers to anode or cathode as A or K. This makes it look like there's too many A segments. Compare it to the other versions, and they have their common pinning on 4 and 5.

Thanks for your help guys :slight_smile: