On a sunny day (Fri, 31 Jul 2009 05:59:39 -0700) it happened Joerg wrote in :
Only when many kHz, I have it drive a MOSFET at about 19kHz directly. How high a frequency does a solenoid need? Not much I suppose?
Yea, take no chances, PIC may present problems if you are not very used to it.
pullup
I don't know PICs, mainly just MSP430 and some 8051 variants. Don't they have a POR/BOR in there that takes its time after VCC gets applied?
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19kHz would suffice here.
I don't mind a new uC but there are some concerns as to the POR/BOR stuff in there. For example, all that TI says in their MSP430 datasheets is 2000usec max. That's a bit longish for this app, by that time there could be some smoke development ;-)
-- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
Then program one of those SOT-23 PICs.
John
How much time between "thumps"?
...Jim Thompson
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| James E.Thompson, P.E. | mens |
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Yes, very tempting, this is what Jan also suggested. Got to find out whether they make one that can wake up from zero power state in under
100usec though, no internal POR/BOR and stuff or where I can disable that. But it needs to be for automotive temps and ideally mask programmable later.-- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
In the single-digit milliseconds :-(
-- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
Trivial. Study what I posted. Long hold-up time. Easy to modify to your needs. NO PWM needed. Only inexperienced weenies think PWM... that's SO school-book and USELESS ;-)
...Jim Thompson
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| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC\'s and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
I love to cook with wine Sometimes I even put it in the food
Post your exact needs, and I'll sketch it out for you. (Initial current, holding current, etc.)
...Jim Thompson
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| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC\'s and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
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I love to cook with wine Sometimes I even put it in the food
Ahm, don't conclude so fast. The coil cannot always be matched to the rail at hand, or shouldn't be. We ain't got no 120V in this here box. So the coil is meant for only a few volts, on purpose ;-)
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Quit bloviating and post the _real_ performance specs ;-)
...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC\'s and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
I love to cook with wine Sometimes I even put it in the food
It's not cast in concrete yet but something like 24V industry rail with tons of noise on there, coil about an ohm so it can ramp up to 3A or so in a fraction of a msec, then must be held there for a msec or so, then ramped down to hold (roughly 1/5th) in 100usec. All this must fit onto the real estate of a postage stamp and dissipate next to nothing, as in
On a sunny day (Fri, 31 Jul 2009 07:34:43 -0700) it happened Joerg wrote in :
pullup
Yes there is, it all depends on how you program it, there are a number of flags you can set. There is a power up timer that will delay 72 ms (16F648A as an example), but it can be disabled. It is recommended to be enabled when brown out reset is enabled. Perhaps in this situation you need neither.
On a sunny day (Fri, 31 Jul 2009 07:37:15 -0700) it happened Joerg wrote in :
I was looking for the minimum clocks it takes before the PIC is normally executing. that is vague, and depends on the internal oscillator startup time. As you can feed the interal osc to an output pin I see possibilities there too. But I would have to run a couple of test to see how fast it really is. Why not, I will try it now.
P.S.: As mentioned before, there is _no_ supply rail.
-- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
Then you're stuck with the NE555 and a mosfet :-)
--
Failure does not prove something is impossible, failure simply
indicates you are not using the right tools...
"If it doesn\'t fit, use a bigger hammer!"
--------------------------------------------------------------
it.
executing.
That would be interesting to know. If the internal osc structure is too slow providing an external clock would be no problem. In an app like this there also wouldn't be a need to load much to RAM either.
-- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
On a sunny day (Fri, 31 Jul 2009 07:37:15 -0700) it happened Joerg wrote in :
I was looking for the minimum clocks it takes before the PIC is normally executing. that is vague, and depends on the internal oscillator startup time. As you can feed the interal osc to an output pin I see possibilities there too. But I would have to run a couple of test to see how fast it really is. Why not, I will try it now.
OK, measured it on my LED lighting controller, PIC 16F648A, 4MHz internal osc., ftp://panteltje.com/pub/LED_control_box_img_1162.jpg The *software* generated PWM on red output is valid 900 uS after Vdd is valid. But to get to that routine it had to execute about 600 instructions before it got to the soft PWM loop, each takes about 1us, so 900-300 = 600 uS if you did your thing first in the startup routine, say 700 uS including port init and whatever should be doable.
On a sunny day (Fri, 31 Jul 2009 16:14:43 GMT) it happened Jan Panteltje wrote in :
executing.
Oops, 900 - 600 = 300, plus 100 for what you want to do, makes doable in about
400 us, with internal 4 MHz osc, but it can run on a 20 MHz external clock too... that would reduce it to 80 us if everything else stayed the same, but I am not sure that is the case.
So what you're looking for is a peek and hold solenoid driver?
I've looked at the DRV103 you suggested, by the time you add the needed components to make that work, You might as well just construct one of your own. I can think of three methods off the top of my head..
One is to use a dual 555 timer type circuit. Timer 1 is the PWM generator that will drive a heavy switching fet for the coil and timer 2, will be a time delay response to shift the timer 1 duty cycle to lower the voltage at the final end. You simply need 2 calibration points here. Timer 1 needs to be calculated for saturation of the coil, timer 2 switch the pwm duty cycle of the timer1..
Second method. Use a multi package op-amp/comparator to generate a PWM and time delay on to switch the PWM duty cycle.
The third and most likely easy if you have the tools at hand, and that is, programming a 8 pin mini micro. AVR, PIC etc... Those can handle the program very easily.. Also requires a Switching fet of course.
P.S. The uC maybe a better solution because you can place other control conditioners in there with the spare IO pins.
And also, adhere to the standard engineering rules of induction flyback suppression, etc.
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