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Topic: Domino Clock (Read 12 times) previous topic - next topic

chrissv


yes that's exactly what i am using 74HC595, i am just sending Q7 to ser_data_in ( 14 ) to the next 74H.


Hi,
I think you are supposed to wire the Q7* (also labeled as Q7'), pin 9, to the serial input of the next '595. The Q7* pin is specifically designated for cascading the chips.

Check out the data sheet here: http://www.nxp.com/documents/data_sheet/74HC_HCT595.pdf

-- Steven

CrossRoads

I'm thinking that electromagnet and "don't drain the battery" are not going to be compatible as described.
These guys
http://www.flipdots.com/EN/electromagnetic_displays/products/page-10/electromagnetic_status_indicators.html
talk about magnetic memory - So I'm thinking pulse of current flow one direction to flip the display, pulse of current flow the other direction to flip it back.
How does your DIY flip dot work?
Designing & building electrical circuits for over 25 years. Check out the ATMega1284P based Bobuino and other '328P & '1284P creations & offerings at  www.crossroadsfencing.com/BobuinoRev17.
Arduino for Teens available at Amazon.com.

CrossRoads

Designing & building electrical circuits for over 25 years. Check out the ATMega1284P based Bobuino and other '328P & '1284P creations & offerings at  www.crossroadsfencing.com/BobuinoRev17.
Arduino for Teens available at Amazon.com.

stregoi

@ Chrisv : i see now i should hook up the Q7' pin to DS and not the Q7 as i did.

@CrossRoard : i see what do you mean, i drawed my idea, so can you see if it works !



so when the magnet is activated, the to pols of the magnets go away from each other, when the magnet is inactivated, it is then atracted to the metal screw head, and stays there. so i dont know if the H-brigde is necessery, since i am not going to reverse the current.

i am stille strugling with the schematics since i am not that good to electronics.

Can i just switch the LED with the magnet or is there any consideretion i have to take ( outside current and resistans ) ?

CrossRoads

LEDs are limited to 20mA, I don't know if that would be enough current for you or not.
You could leave the LED in place, and in parallel add a higher current driver part like a ULN2803 with its own current limit resistor for the magnet.
The number of windings & wire guage & the core you use will all impact the impedance of the resulting coil & hence its current draw.
For example, measure the resistance of the contacts for a speaker, it will be around 8 ohm for many typical speakers. Your coil winding will have some resistance like that also. So take that into account, take your supply voltage into account, take the voltaga drop across your drive transistor into account, work out your current limit resistor from there.
Or you can do it experimentally - find  a higher wattage variable resistor, put it in series with the supply, the coil, and the transistor, with the NPN transistor like the ULN2803 being the bottom of the string going to ground.
Add a resistor to ground to an input pin, and a switch to +5 so you can make it momentarily high to turn it on.
Dial the resistor to highest resistance, and slowly bring it down until you get your response, or until something smokes :)
Designing & building electrical circuits for over 25 years. Check out the ATMega1284P based Bobuino and other '328P & '1284P creations & offerings at  www.crossroadsfencing.com/BobuinoRev17.
Arduino for Teens available at Amazon.com.

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