Fotios need help with input selector. Rotary switch or Relays? - Page 5 - diyAudio
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Old 18th August 2007, 07:14 PM   #41
Nordic is offline Nordic  South Africa
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I thik maybe part of the problem is good product material, and also proabably very few greek tutorials... for most of the small PIC projects I have done.. it normally took a weekend to get back to flashing LEDS with machine code and quite fast from there... onwards... normally code is large and clumsy at the start... getting smaller as time goes on, and new things learned...

I only have experience with 16f84 and 16f128 and of the second one, I don't yet realy know how to use its ADC part yet... and that probably interests me most... can make nice displays!

But sticking with what you have there...if you leave those four pins accessable, the LCD/PIC can just plug into it later.

please send me a message useing the e-mail button so I can get your address... I have very nice LCD tutorial which teaches at such a basic level you could start up an lcd with switches and resistors and no pic. Infortunately it is to large to post here...
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Old 18th August 2007, 08:18 PM   #42
fotios is offline fotios  Greece
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Quote:
Originally posted by Nordic
I thik maybe part of the problem is good product material, and also proabably very few greek tutorials... for most of the small PIC projects I have done.. it normally took a weekend to get back to flashing LEDS with machine code and quite fast from there... onwards... normally code is large and clumsy at the start... getting smaller as time goes on, and new things learned...

I only have experience with 16f84 and 16f128 and of the second one, I don't yet realy know how to use its ADC part yet... and that probably interests me most... can make nice displays!

But sticking with what you have there...if you leave those four pins accessable, the LCD/PIC can just plug into it later.

please send me a message useing the e-mail button so I can get your address... I have very nice LCD tutorial which teaches at such a basic level you could start up an lcd with switches and resistors and no pic. Infortunately it is to large to post here...
Hi Nordic
Check your mail box to find my address. The next hour (i thing one hour it is enough for this) i will draw the timing diagram to see if there is a mistake in the timing of 556s. As you know this diagram it is a type of graphical emulation of circuit. When it is ready, i will post it to seeing. Of course i leave a extra bus from Q1, Q2, Q3, Q4. Also a pair (i have maked this many times) of eproms programmed with the appropriate code, can drive a display also. For those which don't have experience with logic circuits, may reffered that a counter which drives an eprom memory it is equivalent with a microcontroler with basic functions. I am waiting for the tutorial.
Thanks
Fotios
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Old 18th August 2007, 09:15 PM   #43
Nordic is offline Nordic  South Africa
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sent...3 minutes spare
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Old 18th August 2007, 10:43 PM   #44
fotios is offline fotios  Greece
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Quote:
Originally posted by Nordic
sent...3 minutes spare
Thanks N... Nordic for the usefull docs. I have in my stock two LCDs each one of 4X20 characters. I will experiment with the aid of the 2 articles. Hey, may you are Greek? Your name put me in such suspicion.
Thanks again
Fotios
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Old 19th August 2007, 08:30 AM   #45
Nordic is offline Nordic  South Africa
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Glad to be of help...

I am an obvious, blue eyed european... my roots are Flemmish if I understand correctly. So sadly Greek is greek to me... in fact so is Flemmish... My family has been In South Africa for a few generations and our homelanguage is the highly endangered Afrikaans. Although our mix of local peoples also helps us being truly bilingual, on a first language level.
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Old 19th August 2007, 09:06 AM   #46
fotios is offline fotios  Greece
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Default Further improvement of digital selector

I have draw the timing diagram for the state of each in/out point and of each bus internal in circuit. As i said a such type diagram (of same type included in the data sheet of each logic device) it is usefull because offers a graphical emulation. My conclusions from the study of it, are: The most difficult and unpredictable phase it is during power up. As we know, all the 556s drives his output in high state momentarilly during power up; and of course the 556F in the previous post diagram enable thus all the 4066s directly from the moment of powering up; then any false signal produced during the first microseconds and before the 5sec reset cycle completed can be pass to coils. Thus, there is the danger for example, of simultaneous supply of the set and reset coil in the same relay which may cause a mechanical damage in the latching mechanism. To avoid this, for safety may included an auxiliary device which will prohibits the enabling of 4066s for 1sec at least from the moment of powering up the whole circuit. One second it is more from enough to get all the logic ICs her predictionable state by the power on reset of 5sec. This device can be a simple PNP transistor with a RC network in his base of a time constant of 1sec, connected in a such way to prohibit the main enabling NPN transistor of 4066s to not forward biased (on) for this one second; and the connection method it is well known: the base of NPN connected in the emitter of PNP which of collector it is grounded. Later i post the revised schematic.
Fotios
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Old 20th August 2007, 04:20 AM   #47
Bonsai is offline Bonsai  Taiwan
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A micro is a good way to controll the relays.

1. Just make sure you spend some effort to minimize RF coming from the micro. This means RF beads on the lines to and from the coils - these should be positioned carefully so as to attenuate any junk from the controller. Use some resistance and capacitance as well on the relay coil lines if you can (22 Ohms1nF). The caps should be connected to the digital ground plane and the filter located at the exit from the controller circuitry.
2. Ensure th e contrller and associated circuitry is well screened
3. The power supplies for the relay coil and th e controller must be completley isolated from the analog supply and mechanically they should be as far apart as possible to reduce capacitive coupling.
4. Regulate the voltages to the relay coils (LM317 ok for this purpose). Its important that there is no ripple on the relay coil supply as this will generate magnetic fields = noise
5. Place th e catch diode (1N4148 is ok for small signal low energizing current realys) right next to the coil. This reduced the area of th e radiation loop when the coil is switched.
6. Place a small cap (0.01uF) in parallel with the diode and right next to it to further reduce radiated noise and switching clicks
7. As someone has already mentioned, use good quality sealed telecom relays.
8. There is a very good book about noise reduction and grounding etc by a guy called William Ott.
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Old 20th August 2007, 05:35 AM   #48
KISS is offline KISS  United States
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555's are almost impossible to work with on power up. National got rid of the perfect timer (LM3905). A JFET tied to a voltage divider on the gate creates an effective short until the voltage goes above Vgs.

Put the S-D junction across the cap. It will keep the cap shorted before power up. Charge the cap through a resistor to get the time constant. If you need a good edge use a schmidt trigger or comparitor. If you can short out the cap at the end of the pulse as well, it becomes very reliable. It had all the right logic except for the JFET.

Look into voltage detectors too, such as these http://www.rohm.com/products/shortfo...l_index3a.html

and don't forget the reset generators like these:

http://www.maxim-ic.com/appnotes.cfm...te_number/720/
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Old 20th August 2007, 07:35 AM   #49
fotios is offline fotios  Greece
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Quote:
Originally posted by Bonsai
A micro is a good way to controll the relays.

1. Just make sure you spend some effort to minimize RF coming from the micro. This means RF beads on the lines to and from the coils - these should be positioned carefully so as to attenuate any junk from the controller. Use some resistance and capacitance as well on the relay coil lines if you can (22 Ohms1nF). The caps should be connected to the digital ground plane and the filter located at the exit from the controller circuitry.
2. Ensure th e contrller and associated circuitry is well screened
3. The power supplies for the relay coil and th e controller must be completley isolated from the analog supply and mechanically they should be as far apart as possible to reduce capacitive coupling.
4. Regulate the voltages to the relay coils (LM317 ok for this purpose). Its important that there is no ripple on the relay coil supply as this will generate magnetic fields = noise
5. Place th e catch diode (1N4148 is ok for small signal low energizing current realys) right next to the coil. This reduced the area of th e radiation loop when the coil is switched.
6. Place a small cap (0.01uF) in parallel with the diode and right next to it to further reduce radiated noise and switching clicks
7. As someone has already mentioned, use good quality sealed telecom relays.
8. There is a very good book about noise reduction and grounding etc by a guy called William Ott.
Hi Bonsai and KISS
I have already revised my first approach for the input selector. I am intended to replace the logic circuitry with a PIC16F877 as i have the programmer MPLAB ICD in my bookshelf for 6 years. So i can include and a display. The difficult part of the code it is only the part for driving the display. My problem it is the development of code, because i haven't learned never the RISC language for PICs absolutelly, and the last time i had engaged with MCU it is before 3 years. So i have forgot the few things that i knewed and i haven't so much time to spend for revision of books. We see. Maybe one friend has the kindness to help me. The relays that i have choose are this type of OMRON: G6AK-234P-ST-US 5V. You can find informations for these double coil latching relays not from the OMRON site but from Farnell or RS components sites. Because one image substitutes one thousand of words, i quote bellow the block diagram of preamplifier to be comprehensive better my way.

Click the image to open in full size.
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Old 26th December 2010, 12:31 PM   #50
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Bumping this old thread. Looks like Fotios is done with his design.

Post your Solid State pics here.

Over in the solid state forum above, he posted a link to his
interesting PIC 16F887 project, indicating he was open to a group buy.
Here is the link with all details -

MICROS

(Edit: Oops. meant this to go in the analog line forum)

Last edited by quadtech; 26th December 2010 at 12:38 PM.
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