If what you have 'right now' is working what do you want to change?
electronically controlled variable speed pulse generator?
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16th April 2012 09:37 PM #1crosslakeguy
electronically controlled variable speed pulse generator?
I need a two speed (both high and low speed adjustable through trim pot) oscillator. to drive stepper motor pulses. right now I am using a 555 ic the low speed I have a pot where one resistor is and a relay to bring the other resistor from 1k resistor to 0 k for high speed. my motor is running anywhere from 30rpm to 300 rpm its a standard i think 1.8 degree step so 200x whatever rpm x60 for pps.
so running at 30-100rpm for low speed then around 100-350rpm for high speed
adjustable low and high, and switchable between high and low.
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16th April 2012 10:47 PM #2alec_t
0My circuit designs should be regarded as experimental. Although they work in simulation, their component values may need altering or additional components may occasionally be necessary when the circuit is built. Due safety precautions should be taken with any circuit involving mains voltage or electrostatic-sensitive components.
Alec's First Law:-
Every problem has a solution (given the right information and resources).
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17th April 2012 01:01 AM Thread Starter #3crosslakeguy
well....... not sure if there is a simpler way to do it? is there an IC that allows isolated resistor to be used in a circuit? I used a trim pot in series/reed relay. I looked at other forums, and someone wanted to use a series of resistors to do something similar but didn't see a solid answer. I tried a 4066 relay Ic but that did not work. I guess I was thinking about getting away from the reed relay. I know I could have just used a plc, but am not familiar wth the programming, and wanted to keep it simple. also I may want to eliminate the pots, and use an up/down button for speed control.
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17th April 2012 03:39 AM #4
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17th April 2012 05:48 PM Thread Starter #5crosslakeguy
right now (RA) is a fixed 1k resistor and (RB) is a 1k trim pot to control speed. then added a dip relay to make 0 ohm connection between pins 6-7 (RB) which increases pulse speed as noted in osc. I think pin 7 is supposed to be the center on the trim pot then 6&8 on other sides ? I do not have it wired that way,, I have 2 seperate resistors. and was planning on using 1k trim pots on (RA) and (RB) currently using option (2) for (RB). when 0 ohms across pins 6-7 makes the high speed. It works but seems that there is a better way to do it? (the (RB) value may not be a 1k I am not home, but I think it is a 1k?
DSCN0983.JPG0
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17th April 2012 06:07 PM #6Roff
There are lots of ways to do this, but starting with what you have, you could replace the relay with one section of a 74HC4066, and control it with a 5 volt signal. 5V turns it on, 0V (ground) turns it off. Remember to connect pin 14 to +5V and pin 7 to ground. If you don't need the other switches in the package, put all of them in parallel, and drive all the control inputs with the same signal.
Originally Posted by crosslakeguy
If this were my circuit, I would scale the pots up to 10k or 100k, and the 10uF cap on pin 6 down accordingly (1uF or 0.1uF). This is because you need a resistor in series with RA to protect pin 7 from a short to +5V when the pot is cranked to zero ohms. You could add 100 ohms, but that means pin 7 has to sink 50mA, which is kinda high, IMHO.
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17th April 2012 08:07 PM Thread Starter #7crosslakeguy
I did try to use a 4066, but could not get it to work for some reason??will a resistor feed through a 4066 as resistance? Thats why I used a relay, to isolate completely?
I can definately change the value of (RA) and (RB) and the caps for the correct balance/protection....the pulse signal is unbalanced anyways. so all that aside . is there a better way to acomplish an dual speed setup. I can get by with 1st slow speed (able to adjust speed on fly) and high speed fixed but adustable for setup/one time0
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17th April 2012 09:28 PM #8Roff
The 4066 will work if you connect it correctly. The switch is isolated from the control. 74HC4066 has much lower on resistance than CD4066.
I'm assuming you want the low speed and high speed controls to be noninteractive. You need to tell us what the actual pulse frequency needs to be for , say, 300RPM.
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18th April 2012 03:12 AM Thread Starter #9crosslakeguy
hertz=1pps / 60,000 pps, is that 60khz? so I have used a mc104066, and think the 74hc4066 has similar values, the question remains..................
does the resistance carry through???? , you recommended changing the values of the resistors, is that because of the limits of the circuit? a mechanical relay has no resistance at all. is there a circuit that will induce a specific resistance into a circuit? , and is there a better way of a 2-speed controler? as far as interactve? not realy. same circuit, different speed low(adjustable)/switched high.0Last edited by crosslakeguy; 18th April 2012 at 04:38 AM.
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18th April 2012 04:22 AM #10Roff
Yes, Hertz (Hz)=cycles per second. How does 60kHz relate to the RPM of your motor? Originally Posted by crosslakeguy
What do you mean, "does the resistance carry through"?
The 74HC4066 ON resistance is only about 50 ohms per switch. This is insignificant relative to 10k.
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