On Fri, Dec 10, 2010 at 08:51:51PM -0800, Kirk Wallace wrote: > On Thu, 2010-12-09 at 22:26 -0800, Kirk Wallace wrote: > > On Thu, 2010-12-09 at 20:06 -0800, Kirk Wallace wrote: > > ... snip > > > I also wired this up: > > > > > > +--------- O'Scope > > > _ _ | > > > _| |_| | | C1 .01uF > > > -----------\/\/-----+---||--+ > > > R1 15k | > > > V (gnd) > ... snip
> Here is what I have on the bread board now: > http://www.wallacecompany.com/machine_shop/EMC2/chpmp-4a.png > > I changed C2 from .1uF to .33uF. The 1kHz pumped voltage is now a little > higher, ~4 V with very little ripple, and the decay rate is about the > same. So I want to go to the next level. > > Here is my latest stab at an all analog charge pump: > http://www.wallacecompany.com/machine_shop/EMC2/chpmp-5a.png Kirk, that circuit has a small problem. Since OK1 can charge C1, but not discharge it, the circuit is hard put to produce any output. (If you refer back to the fluid pump analogy, you can drive the piston up, but not down.) Adding a pull-down resitor to OK1's emitter, followed by the 3 spare CMOS gates, wired in parallel, will provide the required push-pull drive to C1. (And remove the problem of wasted gates.) If you're ordering some parts, then an IC socket is useful while mucking about. > I'm thinking the opto-isolator on the input might be a good thing, but > using an IC for one gate seemed kind of silly so I was thinking a FET on > the output might work. I have no idea if the output circuit makes any > sense. Comments are welcome. The original approach, using schmitt trigger gates, was better, because that provides a clean transition from "bad" to "good", over a narrow input voltage range. The FET will gradually sag from one state to the other as the voltage on C2 decays. To provide a "window comparator" function, similar to the effect of a PLL tone detector like the NE567, or a suitably programmed AVR, just connect the two comparators of an LM393 like so: +5v |\ | +5v-Ru--|-------------|+\ 2k2 GND-Rv--| e.g. 3v | \ | | \_____| # It's open collector | / | # so the outputs make | / | # a "wired AND" here. >From C2 -------|------|-/ | | |/ | | LM393 | | |\ | |------|+\ | | \ | | \_____|______ High => 1v < VC2 < 3v | / GND-Ry--| e.g. 1v | / +5v-Rx--|-------------|-/ |/ N.B. Input is to inverting input on the high threshold comparator, and non-inverting on the other. Since the voltage references are ratiometrically derived from the power supply, this'll track supply induced variation in the voltage on C2. It will detect variation in mark-space ratio, even if the input frequency does not also change. In detecting changed software behaviour, that can be an asset. It may even work reasonably well for you, with thresholds set to (not too closely) bracket the normal voltage on C2. :-) > I'm still working on a tone detector and AVR version. One benefit of that is that window detection is not subject to component tolerance, or drift with ageing, so long as we don't rely on the on-board RC oscillator. (If a crystal is being used, its drift will be very much smaller than the allowed input variation.) and also On Fri, Dec 10, 2010 at 09:08:54PM -0800, Kirk Wallace wrote: > On Fri, 2010-12-10 at 20:51 -0800, Kirk Wallace wrote: > ... snip > > I changed C2 from .1uF to .33uF. The 1kHz pumped voltage is now a little > > higher, ~4 V with very little ripple, and the decay rate is about the > > same. > ... snip > > Oops, I forgot to mention, the larger cap helped with the DC high input > signal. Part of my testing is to check the output for a 0V DC input to > test for no signal or shorted to ground. Then I tie the input to +5V for > the input shorted to a supply. The .1uF C2 cap would show a ~2V spike > when I made the +5V DC connection, I get nothing with the .33uF C2. I'm not sure that I follow the details of this, but the basic charge pump already checks for DC input (i.e. loss of oscillation), including short to either rail. If C1 is not actively driven high and low, then there is no output. If some of the components for experimentation are coming off old circuit boards, then it's a great idea to test them first, as you're doing. Erik ------------------------------------------------------------------------------ Oracle to DB2 Conversion Guide: Learn learn about native support for PL/SQL, new data types, scalar functions, improved concurrency, built-in packages, OCI, SQL*Plus, data movement tools, best practices and more. http://p.sf.net/sfu/oracle-sfdev2dev _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
