Recent content by Randomly

Very nice work Peter. A slice of engineering heaven. Also thanks for posting the pictures and write up, it's much appreciated. One thought I had about having 50 opto isolator outputs ganged together is that leakage currents could become a problem at high temperatures since they are multiplied...

The transistor level shifter is a current driven system, so it's relatively immune to dv/dt problems. Capacitances are so low compared to data rate that it should also be fairly immune to inter cell inductive spikes (output capacitance of small signal transistor is only around 5pF). In the...

Read the thread. Per cell CPU approaches have been proposed and some people have tried implementing them. I'm not sure what the status of those projects is. Last I remember there was some problems with spikes on the supplies reseting or glitching the processors. You can use a transistor and two...

Yes, a switched flying capacitor sampler would work but you run into the problem of finding integrated FET switches with enough voltage rating to do the job. They seem to max out at about 40V. That's what this schematic essentially is, a flying capacitor sampler that has been simplified and...

Ok, here's a scheme to sample the cell voltages for the A/D converter on a single MCU system without having any current drain on the cells when you aren't actually reading them. The schematic is not complete, it's just enough to explain the concept, you'll need to add the rest of the cells and...

and they are pretty. I'm curious as to what software you are using to generate them? Although I suspect the fact that they look so good is more dependent on your good artistic sensibilities. nice work.

The schematic looks pretty good. You can drop the bottom LT1990 and read the lowest cell voltage directly. You also can just go with the 10 bit A/D in the cpu which will give you ~5mv resolution. 12 bit isn't really necessary. You are always going to have the slow battery drain from the Diff...

That was what I suggested in the last paragraph of the previous post. The LT1990 works the same way the AD628 does, but it's cheaper.

yes it has clamping diodes and if you limit input currents with resistors it won't destroy the part, but you will be getting large amounts of substrate current injection and I don't think they guarantee that the part will perform properly while it's clamping pins. It's very likely some of that...

I figured you'd be calibrating it. It doesn't make sense not to take advantage of such a powerful tool that an MCU with EEPROM makes available. I just wanted to reinforce the fact that the accuracy of a resistor divider system will be very dependent on resistor tolerances. an ATMEGA168 has a 10...

Heya Sheriff Jon! :) I don't know if it's more technical, but it's more electrical. Pretty schematics too. There's lots of interesting around this place, read Ho!

You are going to have to watch out for the Common mode voltage rejection errors of your diff amp from resistor mismatching. Also the matching of the Mux channel resistances. You're also going to have more than 45V across your bottom MUX from Ch1b to ch16b when those channels are off. Similar...

There are a few problem areas to the approach. If you need a 20:1 divider to scale the voltages to the A/D range you end up reducing your A/D resolution by 20, you amplify the effects of thermal drift by 20, even the resistor voltage coefficient amplified by 20 starts to be a noticeable error...

these days most everything is surface mount, many newer ICs only come in surface mount packages. You might try using something like this http://www.futurlec.com/SMD_Adapters.shtml A good fine point soldering iron or hot air tool can be very useful. some SMD info...

An inductor between the Power FET and the battery (and a freewheeling diode to handle the current when the FET turns off) would essentially turn it into a step down converter. The Inductor will allow you to actually limit the current effectively without dissipating too much heat in your FET and...