Phil:
I saw your Optp-isolators. They have much "legs" to me, why not try the 4N25 ones? Just 6 legs (4 useables) ! I think it´s possible on one sided...
Phil:
I saw your Optp-isolators. They have much "legs" to me, why not try the 4N25 ones? Just 6 legs (4 useables) ! I think it´s possible on one sided...
4N25's might work, but the problem I have is the might portion. There are some spec issues that concern me driving straight from a parallel port.
Phil
Hi evreryone, sorry to barge in on this thread, but I would like to build tachus42's Chopper Adapter and am having trouble getting a hold of the small signal transistors. I was wondering if anyone could help me with a substitution?
I need a substitute for the PNP trnsistor: BC556
and for the NPN transistor: BC546B
Also, I think that the 10V zener (D6) should be at least 1W type.
Lastly, theIRF9540 costs $4 each ($CDN). Could I substiture a IRF 9530 (only $1.50 each). I think the main diff between the two is that the 9530 canonly do 12Amp, while the 9540 can do 23Amp. I don't plan on anything more than 3amp motors at most.
Thanks in advance for any help.
Heyarnold,
This thread is open to all who have questions or want to use the boards. Off the top I don't see anything that would be an issue with th 9530. Subs for the BC series, you might look through past postings, seems like this came up before. Tachus43 really should answer that one.
Phil
Hi Phil,
Thanks for you reply, you were right. I did find the post with the BC transistor subs. I pasted it below for reference. I think that I will build the chopper board with 2N3904 and 2N3906 transistors and use the IRF9530 FET as well. I have these in stock!
My plan is to use the chopper with the kitsrus stepper kit #179, which uses the IRFZ44 FETs to drive the motor. I have had this kit for a long time and it works well. I think it will be all right with the chopper board.
Thanks for you help!
Posted by: tachus42 on 08-29-2004, 11:16 AM
The transistors are not critical, most small signal transistors in a
to-92 should be ok.Just check the pinout on the datasheet. For the
NPN BC546,547,548,549 A,B or C will all work. Like wise for the PNP
556,557,558,559 are ok. NPN 2n3904 PNP 2n3906 would be another
choice.
Oh and i don't think the power rating of the Zener was specified on
the schematic. It should be 1 Watt.
heyarnold the 9530 will be fine, but due to it's higher on resistance compared to the 9540 it will get a bit hotter and will probably require a small heatsink.
The kits r us board is very similar to the "open source" design and should work fine with the chopper.
I haven't looked at the spec sheet for the 4n25 lately but it is a pretty slow device. It is for instance useless as a isolater transmitting Midi data at 19200 baud - I tried that and failed!
So I think apart from the current transfer ratio it would be to slow for a Bob.
tachus42,
Yes the 4n25's are slow, that was one of my issues. They get slower as you reduced the led current. I believe 6n138's are a better choice. Know of any others? There used to be some dual channel hpcl's in an 8 pin pack, but I can't find a source to purchase.
Phil
Look another gecko look alike... has anyone seen these?
http://www.linengineering.com/our_products/r701.htm
Kinda looks that way, wonder what they cost.
Phil
Phil was it you or someone else who posted that they thought the need for opto's was over blown? Apart from possibly solving some noise issues it would seem the biggest danger to the PC port is ground currents. With the 10k filter resistor and 1k pullup and assuming the parallel port is ok with 5mA of sink/source above and below it's supply (safe for all logic family's I have seen) either 50 volts would some how have to appear on the hc14 input or the logic supply would have to go to +10 or -5 volts for there to be a problem - both of which seem to be unlikey.
Some zeners, series resistors and a fused earth line should provide pretty good protection for the pc.
OKay. The skinny on this is that they are made by gecko for Lin Engineering. I didn't inquire about the cost.
tachus42,
I have made comments along those lines. As long as the grounding is treated appropriately, there really shouldn't be an issue in not having opto isolators. I suspect that people that have had problems, have their control electronics power supply floating and no reference back to the pc's parallel port gnd lines.
Phil
Ok i agree that we don´t need Optos, but it is a really good stuff. When everything fails, your PC still has a LPT...
A friend, Maarten send me mail about optos, there it is:
Indeed there are other optocouplers (~isolators) that are faster.
The ton of the 4N25 is 5us, the toff is even 10us. This means that you need 5us to reach a full ON (= "1") and 10us to switch it off again. so the maximum frequency is much less than 66kHz (1/(10+5)us = 66,67kHz; and you need time for the pulse itself; the "1"or "0")
There are faster ones like the 6N138 or CNX62 (3 / 3us) or PC816 (Sharp; 4 / 4).
Also TIL111 and TIL112 (resp. 5/5 and 2/2 ) are pretty fast. But the Uce Umacx of the TIL112 is pretty low 20V.
And the Current Transfer Ratio is low (TIL12 (atleast) 2%).
Toshiba has a few super fast ones, like TLP 555 (<=0.4 / <=0.4us; U<=20V)
So every part has its advantages and disadvantages...
Maybe its best to try what best suits your needs.
BR, Maarten.
Interesting,
Maybe I looked at a 4n45, because I was thinking much slower which the 4n25 is. e. I'll look at it some more.
Phil
I am in the process of building my second machine, Jgro's plans only a little smaller. I was looking at the circuits and wondered which set up would be the best to use. I will be using 2A steppers.
I could manufacture all of them, I am an electronics engineer (but not motor drivers!) and use a bungard cnc mill at work. The last circuits I used were hans wedermiers (?) 297/298 circuits which worked well although a bit noisy. What are the advantages/disadvantages of the circuits? and are the Eagle files available?
Thanks Paul
Eagle files are available. Unipolar or bipolar?
Phil
all my motors are unipolar
Paul
sorry, just checked my original 3 are unipolar my spare 3 are bipolar but I can swap and change
Paul (chair)
How did you run a unipokar with the L297/8 combo?
I left the common centertaps unconnected
Paul