#garfield Logs

Mar 06 2020

02:08 AM polprog: rue_mohr: yes, first attepmts had the resistor at the gate, but these didnt work. After i added the diode, it clicked immediately. In my case the gate resistor actually made it not work (voltage drop on the resistor caused the gate voltage range to drop to 0-1.5V or even less)
08:32 AM rue_bed: yea, I was confused that I needed it, I'd have thought that a steady voltage would have been better
09:23 AM polprog: i tried to make a discharge thyristor osc but i cant seem to get it to oscillate
09:23 AM polprog: might need a schmitt trigger but then its kinda pointless. I was hoping it could be done with a 1 thyristor
09:32 AM rue_mohr: because of the way the trigger works, you have to unlatch it by bringing the voltage on the cathode up
02:34 PM polprog: yeah, i figured that
02:35 PM polprog: the hct14 charge pump looks awesome
03:00 PM polprog: how was your day?
04:29 PM polprog: might have made nohit get one of these spartan boards we have
04:31 PM Tom_L: who?
04:31 PM polprog: a guy from #avrs
04:31 PM Tom_L: oh
04:32 PM Tom_L: i left avr and avrs
04:32 PM Tom_L: too much bickering
04:32 PM polprog: i dont think he talks in the old avr channel
04:34 PM polprog: rue_mohr: i was hoping it unlatches itself by fully discharging the cap
04:34 PM polprog: but it seems to top it up and just stay there
04:35 PM polprog: maybe its a holding current issue, the discharge resistor is keeping it on
04:35 PM polprog: but it tried even 1M, and nothing changed
08:02 PM rue_bed: polprog,
08:03 PM rue_bed: if it tops it up and stays there, the discharge cap is too small
08:03 PM rue_bed: the idea is that the charging of the cap causes the available current to drop off below the sustain of the scr
08:03 PM rue_bed: aka, charging the scr is what keeps the scr on
08:03 PM rue_bed: er, charging the cap keeps the scr on
08:04 PM rue_bed: when the scr finishes charging, there is not enough current to keep the scr on, it lets go, and the voltage on the cap can start falling again
08:04 PM rue_bed: play with the trigger voltage, and current
08:05 PM rue_bed: as I said , on mine I needed a high resistnace on the gate
08:27 PM rue_mohr: polprog, if the osc worked by the active component discharging the cap, it would be a relaxation oscillator
08:27 PM rue_mohr: this is the opposite
09:05 PM rue_shop1: ok
10:49 PM Tom_L: what's up tonight?
10:50 PM Tom_L: wonder if z will get a job at spacex...
10:50 PM rue_mohr: I got the 10 pcs HIP4081 form china
10:50 PM rue_mohr: or if he will inherite a million bucks
10:50 PM Tom_L: my kids machine parts for them amongst others
10:51 PM rue_mohr: oh, neat
10:51 PM rue_mohr: 5 of HIP4081 are bad
10:51 PM rue_mohr: 1 is a complete dud
10:51 PM rue_mohr: 4 of the others intermittently fire the fets
10:51 PM Tom_L: defence contracts, gulfstream, spacex for a few
10:51 PM Tom_L: huh wonder why they are bad
10:51 PM rue_mohr: :)
10:52 PM rue_mohr: I didn't pay enough
10:52 PM rue_mohr: $1.40ea
10:52 PM rue_mohr: :/
10:52 PM Tom_L: is that the one rif was using?
10:52 PM rue_mohr: yes
10:52 PM Tom_L: i got mine from dk iirc
10:52 PM rue_mohr: I have two good ones from dk
10:52 PM Tom_L: i bet they are good
10:52 PM Tom_L: no clue how many i have but not very many
10:52 PM rue_mohr: I have enough for the cnc
10:53 PM rue_mohr: but I'd like as many as I was sold
10:53 PM Tom_L: one is on the breadboard
10:53 PM rue_mohr: the fets arrived too
10:53 PM Tom_L: likely you won't get more from there for quite a while
10:53 PM rue_mohr: IRFB3206
10:54 PM rue_mohr: its not ebay tho
10:54 PM Tom_L: alot of the US ports are empty
10:54 PM rue_mohr: I can get my money back
10:54 PM Tom_L: i'll still be able to check in with Tom_L[m] from the phone next week
10:56 PM rue_mohr: good show
10:56 PM rue_mohr: you gonna be commenting on mexican drinks for a while then?
10:58 PM Tom_L: no
10:59 PM Tom_L: not going quite that far
10:59 PM Tom_L: still ~18-20hr drive
11:04 PM Tom_L: you couldn't pay me enough to get on a boat right now anyway
11:07 PM Tom_L: i've always wondered how you calculate the number of turns (primary and secondary) on a transformer and know what size wire to use for the application...
11:07 PM Tom_L: considering the current draw, voltage requirements etc
11:11 PM rue_mohr: well
11:11 PM rue_mohr: iron ones are easy
11:11 PM rue_mohr: there is a volts/turn number, 0.5 I think
11:11 PM rue_mohr: and there are wire size charts
11:11 PM rue_mohr: the cores come with charts as to how many turns of what you can put on them
11:11 PM rue_mohr: and, done.
11:14 PM rue_mohr: I suppose I should make my fet driver boards
11:14 PM rue_mohr: not sure if I want to etch them or not
11:14 PM rue_mohr: x5
11:14 PM rue_mohr: seems like etching them is an idea, its enough volume
11:14 PM rue_mohr: for the convienience of "just drop in the parts"