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https://github.com/openglow-org/forgefirm.git
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ScottW514
8fa10f7b28
Records why the temperature formula changed (and that everything derived from the old one had to be re-derived), the flow characterization data at both heater duties, the false negative that killed the dT-threshold design, and the downstream-rise check that replaced it. Adds flow_characterize.py to the bench kit.
122 lines
4.1 KiB
Python
122 lines
4.1 KiB
Python
#!/usr/bin/env python3
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"""Characterize the coolant flow signature using the FACTORY temperature
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curve, and recommend flow-fault thresholds.
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The loop heater sits between the two water sensors; flowing coolant
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carries its heat away, so downstream-minus-upstream settles at a small
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stable delta. Stopping the pump lets that heat pool, and the delta
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climbs. This measures both signatures and prints the separation.
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Phases: baseline (heater off) -> flow (heater on, pump on) -> no-flow
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(pump off) -> recovery (pump on). Restores heater off / pump on.
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Run with the controller stopped, or accept that it will fight you: the
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driver only writes the heater on M8/M9 transitions, so an idle driver
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leaves this alone.
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"""
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import math
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import subprocess
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import sys
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import time
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HOST = '172.16.1.97'
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# Factory B-equation conversion (see kernel-module-glowforge/UAPI.md).
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F = 1024.0 * 1.3
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RD = 10000.0
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BETA = 3380.0
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RINF = 10000.0 * math.exp(-3380.0 / 298.15)
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def degc(raw):
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if raw <= 0 or raw >= F:
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return float('nan')
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r = RD / (F / raw - 1.0)
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return BETA / math.log(r / RINF) - 273.15
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def board(cmd):
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r = subprocess.run(['wsl', '-d', 'forge-yocto', '--', 'ssh',
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'-o', 'PreferredAuthentications=none',
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'root@' + HOST, cmd],
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capture_output=True, text=True, timeout=30)
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return r.stdout.strip()
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def sample():
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out = board('cat /sys/glowforge/pic/water_temp_1 /sys/glowforge/pic/water_temp_2').split()
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if len(out) != 2:
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return None
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d, u = degc(int(out[0])), degc(int(out[1]))
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return d, u, d - u
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DOWN_ABORT_C = 45.0 # never cook the loop while characterizing
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def phase(tag, seconds, interval=10, settle=0):
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"""Log a phase; return the deltas after the settle period."""
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t0 = time.time()
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keep = []
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while time.time() - t0 < seconds:
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s = sample()
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if s:
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el = time.time() - t0
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print(' %-7s t=%3.0fs down=%5.2f up=%5.2f dT=%+5.2f'
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% (tag, el, s[0], s[1], s[2]), flush=True)
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if el >= settle:
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keep.append(s[2])
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if s[0] >= DOWN_ABORT_C:
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print(' ABORT: downstream %.1f C >= %.1f C safety limit'
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% (s[0], DOWN_ABORT_C), flush=True)
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board('echo 1 > /sys/glowforge/thermal/water_pump_on; '
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'echo 0 > /sys/glowforge/thermal/heater_pwm')
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break
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time.sleep(interval)
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return keep
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def stats(name, ds):
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if not ds:
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print('%s: no samples' % name)
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return None, None
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print('%s: n=%d min=%+.2f max=%+.2f mean=%+.2f'
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% (name, len(ds), min(ds), max(ds), sum(ds) / len(ds)))
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return min(ds), max(ds)
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heater_pct = int(sys.argv[1]) if len(sys.argv) > 1 else 10
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heater_pwm = str(int(65535 * heater_pct / 100))
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print('=== baseline: heater off, pump on (60 s)')
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board('echo 1 > /sys/glowforge/thermal/water_pump_on; echo 0 > /sys/glowforge/thermal/heater_pwm')
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base = phase('base', 60, 10, 30)
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stats('baseline dT', base)
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print('=== flow: heater %d%%, pump on (240 s; first 60 s ignored while dT establishes)' % heater_pct)
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board('echo ' + heater_pwm + ' > /sys/glowforge/thermal/heater_pwm')
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flow = phase('flow', 240, 10, 60)
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fmin, fmax = stats('flow dT', flow)
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print('=== no-flow: pump OFF, heater still on (150 s; first 20 s ignored)')
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board('echo 0 > /sys/glowforge/thermal/water_pump_on')
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noflow = phase('noflow', 150, 10, 20)
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nmin, nmax = stats('no-flow dT', noflow)
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print('=== recovery: pump on, heater off (90 s)')
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board('echo 1 > /sys/glowforge/thermal/water_pump_on; echo 0 > /sys/glowforge/thermal/heater_pwm')
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phase('recov', 90, 15)
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print()
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if fmax is not None and nmin is not None:
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print('flow band: up to %+.2f C' % fmax)
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print('no-flow band: from %+.2f C' % nmin)
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if nmin > fmax:
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fault = (fmax + nmin) / 2.0
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print('separation: %.2f C -> suggested fault threshold %.2f C, re-arm %.2f C'
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% (nmin - fmax, fault, fault - 0.4))
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else:
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print('BANDS OVERLAP - flow detection unreliable at %d%% heater; try a higher duty'
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% heater_pct)
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print('restored: pump on, heater off')
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