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Forum Index : Microcontroller and PC projects : LED matrix with CMM, am I going to break the latter?
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| Warpspeed Guru  Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
It certainly able drive high voltage highly inductive loads, such as stepper or ordinary motors, solenoids, and relays. But it is just as happy sourcing power to resistive loads from +5v and higher. Its just a general purpose very flexible and easy to use source driver ideal for a great many different applications. Edited 2020-02-09 18:21 by Warpspeed Cheers, Tony. |
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Turbo46 Guru Joined: 24/12/2017 Location: AustraliaPosts: 1593 |
Yes it could drive the column of LEDs for thwill but not from 3.3 volts. With 1.7-ish volts across the collector-emitter and 1.7-ish volts across the LED there is not much left of the 3.3 volts for a current limiting resistor (read none). So it would need 5 volts as a minimum. But you did say that. It looks like a handy device, thanks for the heads up. Bill Edited 2020-02-09 18:28 by Turbo46 Keep safe. Live long and prosper. |
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| PeterB Guru Joined: 05/02/2015 Location: AustraliaPosts: 639 |
Yes, I know, I said I was knocking off. If you have a look at the 74LVC244A arc welder. Dirt cheap 8 in a pack what more could you want? They also have tristate output so it would be interesting to see if that could be incorporated into a MM buffer. Now I really mean it. Peter |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
Quite right Bill. No problem on the input side being driven from 3.3v CMOS. I think I would be using the UDN2981 source driver powered from either +5v or +12v (on pin nine). And either the matching ULN2801 pulldown chip, or some discrete transistors or mosfets on the low side. I am a bit biased, have a drawer full of each here, used them for years with great success. I have zapped a few of them, and burned down a few more, but that has never killed the driving source, ever. Its never a good idea to use the same supply for the processor that is switching really heavy loads on and off anyway. Cheers, Tony. |
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thwill Guru Joined: 16/09/2019 Location: United KingdomPosts: 3848 |
It must be a hell of a bang if you are going to hear it in Oz ;-) Incidentally is there some historical reason that there are so many electronics hobbyists and presumably professionals in Australia? Or is it that I just stumbled into the internet's version of the Outback - no offence intended. Best wishes from Blighty, Tom Game*Mite, CMM2 Welcome Tape, Creaky old text adventures |
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| thwill Guru Joined: 16/09/2019 Location: United KingdomPosts: 3848 |
Cheers Tony, Can I ask are UDN2981, UDN2981A and UDN981AT the same thing for my purposes? Likewise ULN2801 and ULN2801A? Also since I have an "audience" can I hijack my own thread and ask what the PCB mounted terminal for attaching to with a crocodile clip is called? It must surely exist, but I'm damned if I can identify them for sale? Also I presume there must be a "wire wrap post" component for mounting in perfboard but can't identify what they are called on eBay. Thanks for your patience, Tom Game*Mite, CMM2 Welcome Tape, Creaky old text adventures |
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| Turbo46 Guru Joined: 24/12/2017 Location: AustraliaPosts: 1593 |
Try 'PCB pins' 'wire wrap pins' or 'PCB header pins', but you can just clip on to the component leads. Bill Keep safe. Live long and prosper. |
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| thwill Guru Joined: 16/09/2019 Location: United KingdomPosts: 3848 |
Thanks Bill, but PCB header/pins brings up exactly that, great for attaching a Dupont female connector to, but I find that crocs have a tendency to slip off them and was expecting something more substantial to exist. Wire wrap pins mostly brings up wire wrap sockets. The only individual pins are 500 for 70 GBP which seems rather steep for a glorified nail ;-) Tom Game*Mite, CMM2 Welcome Tape, Creaky old text adventures |
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| Turbo46 Guru Joined: 24/12/2017 Location: AustraliaPosts: 1593 |
Are you talking about these and/or these? Yes the wire wrap pins are a bit expensive, I don't think wire wrapping is used much any more. Bill Keep safe. Live long and prosper. |
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| thwill Guru Joined: 16/09/2019 Location: United KingdomPosts: 3848 |
Thanks for the links Bill. Still not what I was expecting regarding something to attach crocs to. I just thought there would be something more substantial say 2 mm diameter with a nail style head so the croc wouldn't slip off. I've now found "PCB tab terminals" which look like they might work, I don't know if that is what they are intended for though. Game*Mite, CMM2 Welcome Tape, Creaky old text adventures |
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| Turbo46 Guru Joined: 24/12/2017 Location: AustraliaPosts: 1593 |
This type of clip is good for connecting to components: EZ Hook Bill Keep safe. Live long and prosper. |
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TassyJim Guru Joined: 07/08/2011 Location: AustraliaPosts: 5911 |
Here in OZ we like fencing wire. The PCB equivalent is a short bit of left over component lead soldered in as a test point with the end bent over for the clip lead to attach to. I can sell you a jar full if you like but postage would be a bit steep. Jim VK7JH MMedit  MMBasic Help |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
Yup, for our purposes all the same.  The UD pullup source drivers are classed as digital (on/off) devices which is fair enough. The UL pull down devices are just a big darlington transistor which could(?) conceivably also be used in linear analog mode, but also works just fine when switched on and off digitally. Edited 2020-02-10 06:34 by Warpspeed Cheers, Tony. |
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| thwill Guru Joined: 16/09/2019 Location: United KingdomPosts: 3848 |
I've been meaning to get a pair of those ;-) Game*Mite, CMM2 Welcome Tape, Creaky old text adventures |
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| thwill Guru Joined: 16/09/2019 Location: United KingdomPosts: 3848 |
D'Oh! ... Sometimes the simplest ideas are the best. Nah, I wouldn't want you to run short ;-) Tom Edited 2020-02-10 06:39 by thwill Game*Mite, CMM2 Welcome Tape, Creaky old text adventures |
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| thwill Guru Joined: 16/09/2019 Location: United KingdomPosts: 3848 |
Great, and thanks for the extra effort to post the image. Tom Game*Mite, CMM2 Welcome Tape, Creaky old text adventures |
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| PeterB Guru Joined: 05/02/2015 Location: AustraliaPosts: 639 |
G'Day All I agree the UDN2981 & ULN2801 are ideal for driving Tom's LEDs. However, is there a need for the buffer I proposed about 300mm to the North? At the moment I am thinking (slowly) about a 74LVC244 and 8 x 330 ohm resistors to protect 8 pins. I think it is doable but is it worth while? Tom. The reason you have so many people helping is because we Australians like to feel superior to poms so we take every opportunity. Sadly, in about a month after this steep learning curve, you will be feeling superior to us.  Peter |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
The 74LVC244 would make a great "silicon fuse" to keep the nasties out of our precious microcontroller. It does nothing to increase the drive capability, but it could save a few tears in the long run. Cheers, Tony. |
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bigmik Guru Joined: 20/06/2011 Location: AustraliaPosts: 2870 |
Hi Thwill, Test Points? Something like one of these? Test Point Kind Regards Mick Mick's uMite Stuff can be found >>> HERE (Kindly hosted by Dontronics) <<< |
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| PeterB Guru Joined: 05/02/2015 Location: AustraliaPosts: 639 |
Tony Do you remember when RS232 chips were plugged into sockets because people kept blowing them up? What I propose is 3 x 74LVC244 in DIP sockets and 19? 330 ohm resistors all with suitable connectors to be decided. It means the outputs and inputs are on different pins but would that matter? It comes down to how many people are worried about damaging their MM? Peter |
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