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| 10937p-50 chip? |
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| hydrolisk1792:
Sorry about drawing the transistor upside down lol. I did that so the pins were on with where I had it in the schematic lol. I do have the grounds from the schematic also tied to the arduino. I didn't see a point in sawing the arduino in this schematic because that isn't where my issues lie. I think what I'm now trying to ask is what type of displays to use (common anode or common cathode). How to hook them to the circuit (directly, with limiting resistors, with mosfets, with mosfets on the grid and anode drivers)? I've already assumed that I need to use common cathode because the segment drivers say anode in the datasheet... Right now with that schematic, the chip does work. |
| Whales:
I've just been trying to think how you could use the wrong display type (common anode vs common cath) on this chip and get away with it, but my addled brain isn't letting me. Problem (1): voltage swing. The ADx and SDx outputs look like the might be pull-up only (relying on external pull-down resistors), so if you have split rails (eg +5V, GND, -5V) then you should be able to be clever and cheat the voltage directions to light your LEDs. Problem (2): output patterns. This device will strobe the display, but if it does it inverted then persistance of vision will be ruined (all segments except the one you want will light and show digits). You'd have to use external inverter chips to fix this. Given how digital this device is (serial interface and all) I'm surprised there's no internal option or bit to flip to change between common anode and common cathode. The only info I found suggesting the common type is the timing diagram (figure 1 on page 5). The fact the datasheet does not mention the common type suggests I'm completely missing something. Maybe it's just expected to be of one type, or maybe there's some clever way of using either common anode or cathode that I can't figure out. Sorry hydrolisk :( |
| edavid:
--- Quote from: Whales on May 26, 2018, 09:18:43 am ---I've just been trying to think how you could use the wrong display type (common anode vs common cath) on this chip and get away with it, but my addled brain isn't letting me. --- End quote --- You can use common cathode displays with either direct segment drive or non-inverting segment drivers (NPN emitter followers). For common anode displays you would need inverting segment drivers (NPN common emitter). For common cathode, you also need inverting digit drivers (NPN common emitter). For common anode, you need non-inverting digit drivers (logic inverter + PNP common emitter?). They don't bother showing LED drive on the datasheet because it's really intended for VFD drive. |
| hydrolisk1792:
--- Quote from: edavid on May 26, 2018, 02:40:11 pm --- --- Quote from: Whales on May 26, 2018, 09:18:43 am ---I've just been trying to think how you could use the wrong display type (common anode vs common cath) on this chip and get away with it, but my addled brain isn't letting me. --- End quote --- You can use common cathode displays with either direct segment drive or non-inverting segment drivers (NPN emitter followers). For common anode displays you would need inverting segment drivers (NPN common emitter). For common cathode, you also need inverting digit drivers (NPN common emitter). For common anode, you need non-inverting digit drivers (logic inverter + PNP common emitter?). They don't bother showing LED drive on the datasheet because it's really intended for VFD drive. --- End quote --- So if I'm understanding you correctly, if I need to invert the signals coming from the chip, I'd need to use something like a 74hc14? For pull up and pull down resistors, I'd pull the anodes low and pull the cathodes up? For the npn solution I'd hook the base of the transistors via a resistor to the segment and grid driver pins? Thanks for the information you have given so far, it has helped me quite a bit so far. P.s. the only spot in the dataset that show's any indication of using led is on the first page. But that is it. I've scored the Web for a different dataset that might show the led example bit I've gotten no where. That is why I came here. |
| edavid:
--- Quote from: hydrolisk1792 on May 26, 2018, 09:49:42 pm ---So if I'm understanding you correctly, if I need to invert the signals coming from the chip, I'd need to use something like a 74hc14? --- End quote --- That would be OK. --- Quote ---For pull up and pull down resistors, I'd pull the anodes low and pull the cathodes up? --- End quote --- I don't see why you would need them (unless driving a 74C14 or MOSFET). --- Quote ---For the npn solution I'd hook the base of the transistors via a resistor to the segment and grid driver pins? --- End quote --- Yes, but you only need base resistors for common emitter transistors. |
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