Machinist

I'm looking at the FAN3224, a gate driver capable of several amps at 5V to run my MOSFETs. I'll probably play with direct driving them with the ATtiny at first just to familliarize myself.

The original circuit is running some sort of bridge configuration. I've used a 1.6ohm load for years, with wattage set to 14.5 or 14.8. However, the orignal is capable 25w in the lowest output version. I'm not sure what resistance range it's capable of pushing that 25w.

And, yes, the goal is to build a variable DC supply. I'm finding it really interesting. I'm looking at the synchronus inverting buckboost. I think my final version would use half the components of the original.

If I understand this stuff correctly, (real big if), with the convertor pushing negative voltage, I sidestep high side drive problems. My load is dumb resistance so it doesn't matter how noisy or negative its power is.

So the ATtiny has an ADC capabale of running in windowed mode. A lot of the peripherals are able to run independently of the CPU, you can link them up with onboard programable logic called CLC. So, using logic I can tie the ADC to my PWM at pretty fast speeds. It also has a selection of internal voltage references. I'm planning to use some sort of voltage divider for feedback to the ADC, using the logic to vary my duty cycle when the voltage goes out of bounds.

Before I get that far out in the weeds, I need to play with mosfets, pwm, an inductor, and my new scope.

Plan is for the ATtiny to actually mostly be asleep on the battery voltage. The 5V driver IC has an enable pin and goes into bypass mode when it's not enabled. Only when it wakes up will it turn on the 5V.

I want the 5V for the 4.5V gates on my MOSFETs, the OLED display (IIRC, it will also run on 3.3V), and the 20mhz for PWM and ADC.

DC/DC convertor. I'm hoping I can make a synchronus inverting buckboost supply in the neighborhood of 25w/6V max.

I'll be reading up on push-pull. Thank you!

Main power source is a single cell lithium, so 3.7ish volts. Supply for the ATtiny is a 5V driver IC (I've already got it working).

The convertor I want to build will be inverting as the load is basically a pure constant resistance. (14.5w 1.6 ohm typical). I think that means I sidestep all the problems with a voltage higher than my control.

I'm hoping to use the window mode of the ADC and the programmable logic (CLC) to actually control the convertor mostly independent of the CPU.

I'm bumping against the edges of my ignorance here. I haven't done any calculations yet. I've been reading the DC/DC Book of Knowledge by Steve Roberts.

I've got a working 5V switch mode supply using a driver ic for the ATtiny. Plan is to use that supply and the ATtiny to variably control a larger inductor/MOSFETs. This will power a resistive load around 25w max, 14.5w typical, 1.6ohm so roughly 4V/3A typical.

The data sheet gives an absolute maximum of 40mA for output on a pin with 5-10mA being ideal. My understanding of the chart above is that the voltage will also sag below the 4.5V gate actiivation. I'm assuming trying to switch the MOSFETs with just the ATtiny either leads to a blown output or an overheated MOSFET.

I guess I need to figure out my target frequency and work backwards from there. I've got a working reference circut, but all the ICs and MOSFETs have been laser obufuscated. Inductor is 1.5uH and 27A.

So I'm assuming I need a higher frequency than what I can push with the ATtiny but I don't know that.

Sorry for the novel. Writing this down helps me work the problem. Do you see anyrhing wrong in my assumptions/reasoning?

I was thinking bjt or opamp to drive the mosfets, but I'm not sure.

And yeah, I'll be scoping it as I start testing. I'm just still wrapping my head around the synchronus inverting buckboost I think I want to use.

I'm hoping to end up with a pcb that has the features of an obsolete ecig that my spouse and I prefer. I've probably purchased a dozen of them over the years. The switches always fail.

Given the politcal climate towards ecigs (What about the children?!!!!?), my particular harm reduction method continues to become more difficult to source. So, I'm just going to future proof things and build my own. I doubt the design will be worth any money so I'll probably open source it if it works.

So pretty serious about durablility, it would be a tool for daily use. I plan for switches to be on a daughter board so I can just change them out.

I'll be checking out the video this evening.

Thanks!

We already confirmed he was watching porn. I always figured Betty White was absolutely depraved in the sack. Jeanette Nolan must have been a hell of a top, if you're into that.

Not OP.

That sucks. Especially having to make poor people financial decisions, you often can't afford to make changes that will save you money in the long run. Been there done that.

Still, there may be some things you can do to save electricity.

Cheapo line meter. I use one on my well pump. It shows usage over time. You can figure out what's using the most juice. It does 200v as well as 110 and clamps on. Does have to be wired in to for it's power supply and ground.

Also, Kill-a-Watt clones. $9.99. Shows you how much plug in things use.

Offhand things that might help:

• Hot water heater on a timer and turn down the thermostat. There wil be bitching.
• If you have an electric stove, inductance stoves are supposed to be the most efficent, but you probably can't afford one. Electric kettles for boiling water probably beat using a stove to heat water.
• Use a kill-a-watt to figure out what is using juice when appliances/TV/PC/etc. is on standbym
• Check freezer temp, it may be colder than you have to have it, turn up the thermostat.
• Check anything with a motor that plugs in with the kill-a-watt, like box fans to see if they're pulling too much juice, when the motor bearings get shitty, you'll pull more over coming friction.
• Use that clamp meter to check things like whole house blower fans, bathroom fans.

Good luck.

Yeah, I haven't read the article yet, but the headline is certainly inflammatory. Change it to Biden and add some adrenochrome or satanic panic and it's q-nut BS. I just fucking looove that Blueanon is a thing now. Didn't we learn anything from that?

I guess we learned that people are stupid and gullible.

It makes me feel pretty down because it's so fucking hard to steer through the misinfo anymore. Hell, it could even be true. I'm too tired to dig on this one.

Practice information hygiene and stay skeptical!

Check out Red Sparowes, it's instrumental progressive metal (I guess it's metal) that heavily features steel guitar. Very big sound, it's like listening to a landscape or dramatic weather.

I don't give a fuck if it summarized the specs correctly. It's been proven to be wrong often enough that trusting it to be correct when dealing with life and death issues is foolish.

I searched a basic spec to get a link to a manufacturer spec list. The bot offfered to vet my setup for safety. It seems you're suggesting that it's a good idea to listen to a chatbot for high voltage safety advice.

I'm not the one with the comprehension issue here.

I didn't ask for high voltage safety tips from a chatbot. It offered them. If you don't think that's dangerous and wildly irresponsible, you're being disingenuous at best and willfully ignorant at worst.

• 25 year machinist including maintenance

It's not me that's going to be killed. it's people that don't know enough to not trust a fucking chat bot. Do you really trust a bot to explain ground loops, isolation transformers, and floating test equipment? If so, I feel real bad for any kids you might be training.

Fuck 'gemini'. I don't trust a glorified chat bot with life and death advice. Don't be simping for a chatbot ran by an objectively evil corpo.

I don't care what the actual max voltage is. That search was a shortcut to find the manufacturer spec summary while looking at third party probes. Not 'gemini's' summary or anything else. I don't want electrical, romance, or life advice from a chatbot. I want links to relevant resources.