Sciencemadness Discussion Board - Det cap questions: e-match nichrome, selecting a primary

Det cap questions: e-match nichrome, selecting a primary

UndermineBriarEverglade - 13-6-2024 at 18:09

Hi everyone! Just getting into energetics. I want to figure out a safe det cap design so that I can play with secondary explosives.

First, I already built a remote ignition device that uses a digital timer to discharge a 9V battery through a 3Ω resistor. Tape to a match, set it to 5 minutes, get comfortable behind cover. Very precise. However, the resistor sometimes cooks to a higher resistance before whatever it's attached to is set off. Approaching a dud is no big deal with pyrotechnics but scary with explosives.

I'd like to improve it with a nichrome coil as a heating element, dipped in NC lacquer (acetone and smokeless powder) and ground-up match heads so that the heating element and match can't separate. Is this reasonable?
What thickness nichrome should I use? What are you guys using? I'd like to keep the current at 3A - this is a comfortable current for my batteries to provide without dropping the voltage below what the timing chip needs - but that needs a very long length unless I pick a thin and fragile wire.

Second, what can I do to make a SAFE det cap that's not going to explode in my bag on the way to the field? As a beginner I would really rather not synthesize a primary explosive at all. Mineman's pyrotechnic detonator looks a little complicated for me.

Can I make a det cap by cooking off confined commercial firearm primers? I know cartridges can bang around in a backpack forever with no danger.

If not, can I scavenge lead azide/etc from commercial primers to avoid having to synthesize a primary?

I'm probably gonna make ETN for the cap output segment. Are there designs that use ETN as the initiator as well? I read that you have to be careful casting ETN because it becomes dramatically more sensitive while liquid. So perhaps someone has made a cap that melts and detonates a small amount of ETN. DennyDevHE77 says some detonators are made without primaries:

Quote:

All detonators without a primary explosive usually work as follows: a low-density charge of a sensitive secondary substance (PETN or ETN) is affected by a heat flux from a high-temperature pyrotechnic composition (thermite / powder / something else). As a result, layered combustion begins in the charge of the secondary explosive, then it quickly turns into convective (gorenje gorenje gorenje between the particles of the explosive), and then the combustion breaks down into a detonation wave. Therefore, the charge must be low-density in order to accelerate the transition of combustion to detonation

For interest, here are some pics of my pyrotechnics igniter

Sir_Gawain - 13-6-2024 at 18:46

First of all, I would never trust a timer circuit enough to plug it up while holding an explosive charge.

You can cook off ETN but it’s hard to make it reliable. I’ve had some success with initiating ETN with copper oxide thermite (iron oxide just didn’t work).

As for primaries, I would recommend NHN. DDNP also works quite well.

If you are looking for top safety and reliability, build a simple EBW detonator. Using a stun-gun module to charge a microwave oven capacitor to 4kv and discharging through a very thin wire has initiated ETN every single time I’ve tried it(>25 times).

UndermineBriarEverglade - 13-6-2024 at 19:19

Wow that EBW setup sounds easier than I thought. So you're using one of the cheapo ebay modules? Are you using a switch for that 4kV or just touching wires together once it's charged up?

This particular board is only for pyrotechnics: it is designed to fail "on" if it starts to run out of battery. I will have to redesign it with all the safety stuff in the other direction. I'd probably never trust somebody else's gadget - especially all the godawful analog timers - but I'm doing the design/code/assembly/testing myself so I figure it isn't much more risk than the actual synthesis.

Sir_Gawain - 13-6-2024 at 20:54

Yeah, I’m using one of the cheap EBay modules. With a single 18650 the voltage levels out at around 4kv; the bleeder resistor in the capacitor keeps it from going higher.

For switching it, I at first used a triggered spark gap, then switched to a large relay which worked better.

The detonators I use with it are composed of 1 g of ETN: 0.25g very low density, 0.25g pressed, and 0.5g melt cast. The body is made from 0.25 in ID aluminum tube sealed on one end with pressed aluminum foil. The EBW head is made from a 0.25 in long piece of .25 in acrylic rod with two holes drilled in it to feed the wires through, and epoxied in place.

Edit: Here’s a post I made describing the construction in greater detail.

[Edited on 6-14-2024 by Sir_Gawain]

Etanol - 13-6-2024 at 23:27

This is a perfectly selected scheme and its design.
Use a fishing line or a magnetic switch and a magnet to safely activate this.

The best nichrome thickness is 0.15-0.2 mm.

NHN is too unreliable and has a large delay in detonation. I made it in different ways and refused it.
Use HMTD, lead or silver azide, silver nitrotetrazolate, copper diazoaminotetrazolate, Ni-aminoguanidine perchlorate, Ni or Cu 4-aminotriazole perchlorate, Ni or Cu carbohydrazide-perchlorate. These substances do not fail.
Perhaps DDNP, BNCP and Cu glycinate-perchlorate are suitable. I did not work with them.

dettoo456 - 14-6-2024 at 07:04

@UndermineBriarEverglade, are you in the US or EU? If you’re in the US or can order from Alibaba or other pyrotechnic suppliers in your country, I’d recommend just buying the pre-made E-matches (10ft or longer). They aren’t perfect quality and can have duds but are much easier to deal with and are consistent (consistently bad or good) from different suppliers. The e-matches conveniently have a 1/4” OD red cap on the end which helps to fit snugly in whatever 1/4” ID tubing you’d use - just requires a small dab of glue and a crimp to make a strong seal to the cap body.

As for the cap body itself, thin aluminum works well and is used widely in industry but I’d prefer stainless for corrosivity protection and strength. Thermocouple/thermowell/temperature sensor tubes (sealed at one end) are basically perfect for this. Aliexpress has a couple 7mm OD x 50mm length stainless tubes available for a reasonable price.

For an output charge, pressed PETN or ETN (ETN needs to be highly washed and acid-free) is good. Transfer can be loose fill/low density PETN or ETN, and for the initiating charge, I’d use AgNTz.
If you aren’t comfortable making AgNTz, SADS could work (though I don’t know if it corrodes Al or stainless) or try making a perovskite complex from something like AgClO4 or NaClO4 and piperazine.

Also, if this is your first time working with anything energetics wise - make sure you take every precaution you can. Don’t hurt yourself or others.

[Edited on 14-6-2024 by dettoo456]

fx-991ex - 14-6-2024 at 08:11

If you want to do nichrome wire dipped in NC, what i found is NC alone wont do much.
What i do is i dip it in NC lacquer, let it dry, then i dip it again in NC lacquer and then in some black powder(meal powder if possible) i let it dry and then one last drip in NC lacquer to seal it.

I guess black powder could be replaced by other pyrotechnic composition, like ammonium perchlorate or flash powder.

Make sure to solder wire to the nichrome wires, otherwise the resistance will be wrong.

[Edited on 14-6-2024 by fx-991ex]

UndermineBriarEverglade - 14-6-2024 at 10:27

Thanks everyone. Sir_Gawain I really appreciate the schematic and detailed cap design. I'll build something similar. I will spend a little while researching a solid-state solution but high-voltage SSRs are probably too expensive and I've got some beefy relays lying around. What is C2 for, inrush current on the relay? (edit: oh yup I see)

Noted, thank you Etanol. If I can't get Gawain's EBW to work I'll plug this in to one of the length/target temp calculators and probably use it with NC + smokeless powder per fx's recommendation.

Dettoo, I'm in the US, but hate to order anything but the most innocuous components online. I've had stuff seized before so I'm on the customs watchlist already

. I've heard that an inner layer of a plastic straw inside metal caps can be a good idea. I'll have to check compatibility of all the metals I'm using (bridge wire too) with my ultimate choice of chemical. This will be my first time working with EM. I have read the warnings about peroxides, Life after Detonation, etc. I will doing syntheses as small as I can manage, keeping all my appendages away from the work, and using double boilers if I need to heat but would appreciate any suggestions for safety equipment - face shields, etc.

[Edited on 2024-6-14 by UndermineBriarEverglade]

[Edited on 2024-6-14 by UndermineBriarEverglade]

Yorty2040 - 14-6-2024 at 11:00

The copper hexamine perchlorate complex (CHP) is a very safe primary, and easy as shit to make with common pyrotechnic supplies available in the US. You might need to use a bit more of it than you would of a nitrotetrazolate salt or nickel aminoguanidine perchlorate:isopropanol complex if you're trying to set off ETN, but it's cheap and easy to make, so using more of it isn't too big of an issue for most applications.

Making CHP complex:
https://youtu.be/ZV9Pv3Jdtak?si=QtUejgvA7YI9bQYR

If you can't find aluminum or stainless-steel thermocouple covers, the casings of ballpoint pens make a good substitute if you can compress the contents.

[Edited on 14-6-2024 by Yorty2040]

dettoo456 - 14-6-2024 at 20:24

Also, I’d refrain from casting ETN in general. The performance gains are low compared to the waxed, crystalline, pressed material.

And as Yorty mentioned, CHP can be a capable primary, though I’d view it as a better booster than primary, and a fairly weak booster at that.

The primary you use as an initiator is only required in very very small quantities. For example, a 300mg (or larger) pressed PETN output, followed by a 50mg loose PETN transfer charge, only needs 15-20mg of AgNTZ. NAP, SADS, AgN3, or DBX-1 would perform just as well in around that same 15-20mg range.

greenlight - 15-6-2024 at 09:24

I'm still a fan of aluminium cased caps filled with 700mg recrystallised, pressed PETN base charge, 200mg PVA coated lead azide pressed primary and a final layer of granulated milled black powder with the ignition bridgewire nestled into it to ensure ignition.

Have had them stored for 7 years before and they never fail.

Am I getting too old and behind the times these days, is the beloved ead azide not favoured anymore? I know she's toxic and extremely sensitive and more so if not synthesised properly, but she's a damn good initiator with remarkable DDT properties.

ManyInterests - 15-6-2024 at 12:08

Quote:

I'd like to improve it with a nichrome coil as a heating element, dipped in NC lacquer (acetone and smokeless powder) and ground-up match heads so that the heating element and match can't separate. Is this reasonable?
What thickness nichrome should I use? What are you guys using? I'd like to keep the current at 3A - this is a comfortable current for my batteries to provide without dropping the voltage below what the timing chip needs - but that needs a very long length unless I pick a thin and fragile wire.

The way how I make my e-matches is I use a regular match (any size will do) and I put the nichrome wire over it and each wire tapped to the sides (separately, to prevent a short). This has proven to be an extremely reliable way to make an e-match for me and I almost never have any failures.

For the thickness of e-matches. I've experimented with 0.08mm, 0.1mm, 0.15mm, 0.20mm, and 0.25mm. I would not recommend going above 0.25mm since you need a LOT more power to get that to light up vs the smaller ones. the 0.15mm and 0.20mm are the best in my opinion since they are thick enough to be easily managed, but also thin enough to not have to worry about the battery power being insufficient. the thinner ones are simply too bouncy and while they can be used, I would rather use something thicker that is easier to work with.

Quote:

If not, can I scavenge lead azide/etc from commercial primers to avoid having to synthesize a primary?

Theoretically it can be done. I read in ragnar's homemade detonators that it takes around 5 large pistol primers to give enough material to make a detonator. Now I need to make it clear about this, I don't know about that first hand since I never made a detonator that way. I did remove priming compounds from toy caps (I intend to use them to make strike-anywhere matches), and when one goes off (rarely for me) it is a nasty thing. Not injurious I just hate it. I can't imagine how much more powerful a large pistol primer going off will do.

Quote:

Also, I’d refrain from casting ETN in general. The performance gains are low compared to the waxed, crystalline, pressed material.

I was informed that it is much more superior to regular recrystallized ETN (in methanol to give it an extremely fine powdery texture). also would it be generally denser?

dettoo456 - 15-6-2024 at 12:20

Cast ETN is denser and will outperform crystalline ETN, but the gain in performance doesn’t seem high enough to matter. Especially if the ETN is the output charge of a detonator, 100-500m/s difference will not be a big deal. Even 5500m/s or lower EMs can be strong enough to initiate a secondary main charge, so the 7.5km/s from pressed ETN is fine.

And the increase in loading amounts (from simple density calculations) would likely verge on <50mg more in a cast ETN filled detonator vs a pressed ETN filled detonator - not too big of a deal if you’re working with 700mg total output EM.

On the other hand, large charges of over maybe 50g may benefit from noticeable improvements in performance with cast ETN over pressed, but I’d never want to melt that much ETN anyways.

Scavenging primer EMs is a bad idea too. It’s way more laborious and dangerous than just making the EMs yourself.

ManyInterests - 15-6-2024 at 14:37

Quote:

Cast ETN is denser and will outperform crystalline ETN, but the gain in performance doesn’t seem high enough to matter. Especially if the ETN is the output charge of a detonator, 100-500m/s difference will not be a big deal. Even 5500m/s or lower EMs can be strong enough to initiate a secondary main charge, so the 7.5km/s from pressed ETN is fine.

The more powerful the better. I made 6 detonators to test, but due to really cramming my cap bodies (1g of ETN + 0.3 to 0.4g etn/nhn mix) I hope that putting in my ematch didn't press the mixture too much... and that the epoxy I put in doesn't hinder ignition, the only UXO I was a cap that I am certain the epoxy got between the match and the mixture. I took some pliers to crimp the top of the cap, it slipped away for some reason (the steel is quite hard) and even yanked the match out. I hope it'll be OK in the end. I just want them to detonate!

UndermineBriarEverglade - 17-6-2024 at 17:12

ManyInterests, I read that part of Ragnar's too but I think that actually scavenging primary from commercial detonators is kind of sketchy. It would be much nicer to have a way to use the complete primers, since they won't go off from dropping, shaking, etc - basically anything short of a firing pin. I might melt-cast some ETN and then break it up into powder again, but I probably won't bother since it doesn't seem important for detonators.

But I'm going to make Sir_Gawain's EBW design before I make any primaries. Waiting for parts to arrive.

Microtek - 18-6-2024 at 23:11

Firearms primer mixture is much more sensitive than a quality primary such as many of the metal amine perchlorate complexes. Several of these complexes are also less sensitive than ETN, which is quite sensitive itself.

Regarding ETN and melt casting or pressing, you cannot ignore scaling effects: In a large diameter charge, cast ETN would probably outperform a pressed one since a well cast charge would probably be the denser of the two (though it is not a given that a cast charge will be at max theoretical density). However, in smaller diameter charges such as a detonator, the lack of crystal boundaries in the cast charge will increase the critical diameter and decrease the detonability of the ETN (it does this in the large diameter charge as well, obviously but because of the large diameter, critical diameter effects are not noticeable). Due to the high sensitivity of ETN, you would probably be able to initiate it anyway but eg. Roscoe reported difficulties in initiating cast charges of ETN/PETN cast composite.
Taken together, the higher than normal critical diameter of cast ETN, the small diameter of typical caps and the relatively weak containment of cap bodies, you might well end up with caps that perform worse and are less reliable if you cast the ETN.

If you plan on setting off larger charges, consider using redundancies in your initiating train. This way you can square (or cube with three independent systems) the risk of a dud, so for instance a 90% reliable train would give a 99% reliability with two independent systems.

UndermineBriarEverglade - 23-6-2024 at 11:49

Quote: Originally posted by Sir_Gawain

Yeah, I’m using one of the cheap EBay modules. With a single 18650 the voltage levels out at around 4kv; the bleeder resistor in the capacitor keeps it from going higher.

For switching it, I at first used a triggered spark gap, then switched to a large relay which worked better.

Edit: Here’s a post I made describing the construction in greater detail.

[Edited on 6-14-2024 by Sir_Gawain]

Tested it out (no electronic control, no EM yet) and this thing packs quite a punch! I'm using a step-up converter to power the relay from the same battery used for the HV transformer and, eventually, control circuits. But I'm having a problem: as I charge up the cap, the voltage eventually rises high enough to simply arc past the relay. Not sure if it's across the external relay lugs or internally across the contact, but either way it fires after a couple seconds without ever powering on the relay. Did you just use a really wide relay, and/or one with a very large throw? I wonder if I could use several relays in series to increase the total required arc length. I see that there are actually commercial high-voltage relays for pretty cheap as well.

How are you and freepatentsonline actually measuring these high voltages? I have no way to know how charged the cap is or what rated relay I need.

[Edited on 2024-6-23 by UndermineBriarEverglade]

Sir_Gawain - 23-6-2024 at 18:15

I'm using a very large relay that has an open contact gap of about 5mm.

Quote: Originally posted by UndermineBriarEverglade

How are you and freepatentsonline actually measuring these high voltages? I have no way to know how charged the cap is or what rated relay I need.

To measure the voltage, buy a cheap amp meter and wire it in series with a 1 M ohm HV resistor. 1 mA = 1 kv.

dangerous amateur - 24-6-2024 at 06:50

Quote:

If you are looking for top safety and reliability, build a simple EBW detonator. Using a stun-gun module to charge a microwave oven capacitor to 4kv and discharging through a very thin wire has initiated ETN every single time I’ve tried it(>25 times).

That capacitor is very far from ideal imho.
How can you say you initiated ETN 25 ttimes? Did you use a witnes plate or did you just judge the bang it made?

Quote:

With a single 18650 the voltage levels out at around 4kv; the bleeder resistor in the capacitor keeps it from going higher.
[/rquote]

The bleeder resistor or rather the failing capacitor?
Usually those are rated some 2XXXV...

[Edited on 24-6-2024 by dangerous amateur]

Sir_Gawain - 24-6-2024 at 10:55

Quote: Originally posted by dangerous amateur

Quote:

That capacitor is very far from ideal imho.
How can you say you initiated ETN 25 ttimes? Did you use a witnes plate or did you just judge the bang it made?

They were tested against witness plates, but most were using them to initiate ammonal charges. I know the capacitor is very far from optimized. It should be pulse-rated polypropylene film, but somehow the simple oil and paper caps work.

Sir_Gawain - 24-6-2024 at 11:04

Quote: Originally posted by dangerous amateur

Quote:

With a single 18650 the voltage levels out at around 4kv; the bleeder resistor in the capacitor keeps it from going higher.

The bleeder resistor or rather the failing capacitor?
Usually those are rated some 2XXXV...

The bleeder resistor. When it reaches a certain voltage, the resistor drains it away as fast as it charges. You just have to find an input voltage (on the hv module) that makes it level out around 4kv. For me it was 3.7 v from one 18650.
These caps can actually handle way more than their rated voltage (>8kv).

[Edited on 6-24-2024 by Sir_Gawain]

UndermineBriarEverglade - 18-7-2024 at 14:07

I measured my output as 5KV from a 9V battery. Spent $10 on a reed relay rated for 4KV isolation and so far it hasn't arced unexpectedly and seems to be firing properly. Of course you can't buy a 5KV/300+A rated relay anywhere so its lifespan will be limited. The relay can be powered from the same battery running HV converter and the electronics.

Though it makes a nice bang I still have not cooked up any ETN to test if the bridgewire is really capable of detonating it. I've boiled down some sulfuric acid but am having trouble sourcing ammonium nitrate. Found some ammonium nitrate cold packs on Amazon, but how to get them without getting on a list? Going to use nitrate salt instead of mixed-acid method because nitric acid is also hard to obtain.

fx-991ex - 19-7-2024 at 06:02

You can add a capacitor across the relay/switch terminal to reduce arcing and make the contact last longer. Be carefull i dont know if this will be safe with a fuse, i dont see why it would not but better be safe than sorry.

UndermineBriarEverglade - 19-7-2024 at 08:24

To be clear, the arcing I'm talking about was 5KV jumping the terminal before the relay was turned on, not arcing while making/breaking the connection. I'm not worried about relay damage (think it's unavoidable putting that much current through it), just didn't want the thing to go off unexpectedly!

This is what I have designed. Circuit board is size of the microwave capacitor, waiting for it to arrive. There's an green indicator to show that the outputs are electrically disabled and it's safe to plug them in. Before throwing the switches to enable the HV converter and det cap, you check the red/yellow indicators to make sure software isn't trying to turn on the output. But software is still safety-critical in the end. The charge pump overdrives the relay slightly (datasheet says 1.1ms to turn on at 16V).

[Edited on 2024-7-19 by UndermineBriarEverglade]

fx-991ex - 19-7-2024 at 12:16

Nice circuit, good idea the charge pump for the 15Volt supply.
You could probably do without the "driver on" circuit by just disabling the pwm signal, i guess you know all that already.

[Edited on 19-7-2024 by fx-991ex]

UndermineBriarEverglade - 19-7-2024 at 13:16

Yeah it's kind of a kludge, the charge pump uses a few mA in steady state without a disable. It would be better to use a LTC1044 or something but I wanted to test it without waiting for new components to arrive.

UndermineBriarEverglade - 25-7-2024 at 11:20

Charge pump works well to trigger relay and safety mechanisms are adequate. But the HV converter is just whalloping this 9V battery. 2-4V most of the time and ringing to 14V, enough to brown out the microcontroller once it starts charging up the cap. I should have scoped this in the early design phase, I just assumed the source was sufficient based on the output voltage. Even lithium batteries droop too much. I'll need to use a separate battery (like Sir_Gawain) or redesign to feed the small circuitry with a boost-buck converter or some nonsense.

I'll do my ETN synth soon. Why does it have to be so difficult to get nitrate salts, ammonia, nitric acid when you can literally buy POUNDS of arsenic trioxide online.

[Edited on 2024-7-25 by UndermineBriarEverglade]

UndermineBriarEverglade - 8-8-2024 at 12:43

Sir_Gawain, what quantity of ETN are you able to detonate unconfined with your EBW setup? Mine failed to detonate 50mg of loose ETN. I can test initial voltage, but without a way to measure discharge time or current I can't tell if the wire is actually exploding or just melting faster than a camera frame.

Also, based on a candle flame below aluminum foil, I do think a nichrome coil around an ETN cap might be a simpler detonator. Maybe with a little motor to vibrate it.

Sir_Gawain - 8-8-2024 at 14:03

Quote: Originally posted by UndermineBriarEverglade

Sir_Gawain, what quantity of ETN are you able to detonate unconfined with your EBW setup? Mine failed to detonate 50mg of loose ETN. I can test initial voltage, but without a way to measure discharge time or current I can't tell if the wire is actually exploding or just melting faster than a camera frame.

Also, based on a candle flame below aluminum foil, I do think a nichrome coil around an ETN cap might be a simpler detonator. Maybe with a little motor to vibrate it.

While testing, I would add some ETN (<100mg) to a piece of tape, add the bridge wire, and fold the tape over. These little detonators were quite powerful and always fully detonated. 500mg wrapped in tape blew a sizable hole in a steel can.

It’s pretty easy to tell if the wire is exploding properly or just rapidly melting. Set off a bridge wire (about 5 mm long) in air. It should make a loud crack and produce a brief blinding flash. It should also leave a film of vaporized copper on nearby surfaces.

One of the biggest problems with the cook-off type detonator is the tendency to simply catch fire, possibly igniting the main charge. I’ve had it happen to me before, and trust me, a slowly smoldering stick of dynamite is not a fun thing.

UndermineBriarEverglade - 8-8-2024 at 20:17

It does make a loud crack, brief flash, and metal dust deposits. In slow-motion video I get one frame of complete white and then a spray of sparks.

Hmm, that's a good point.

edit: Successful detonation with a slightly larger amount of ETN in tape. Installed new relay after finding the previous one was stuck closed. Contact resistance might have been increased in previous attempts, explaining weak bursts. Maybe I will "flicker" the relay after firing to try and shake off any hot gunk. Reed relays might not be the way to go. Must have been <10 bursts before it died.

[Edited on 2024-8-9 by UndermineBriarEverglade]

UndermineBriarEverglade - 1-11-2024 at 19:22

Sir_Gawain, would you mind posting the model of relay you're using, the approximate number of uses you get out of it, and the resistance of one of your bridgewires? I get maybe 5-6 shots per relay, and that's after melting it unstuck with high current after each shot. I want to find a relay that will last longer, or at least be cheaper and fit a standard socket. Unfortunately this use is so far out of the datasheets all I can do is trial and error with different relays. My bridgewires are about a tenth of an ohm. I found it easier to cut stranded wire down to a single strand instead of soldering nichrome.

Sir_Gawain - 1-11-2024 at 21:26

Quote: Originally posted by UndermineBriarEverglade

Sir_Gawain, would you mind posting the model of relay you're using, the approximate number of uses you get out of it, and the resistance of one of your bridgewires?

I'm not sure of the model, but it's a high amperage relay from an HVAC unit similar to this one. I've fired it probably close to 100 times and while there is some erosion of the contacts, it's not problematic. For the bridgewires, I use 40 AWG wire from a microwave turntable motor. It's hair-thin, and works significantly better than the thicker wire it sounds like you're using. The resistance is too low to measure with my meter (<0.1Ω)

[Edited on 11-2-2024 by Sir_Gawain]

fx-991ex - 4-11-2024 at 08:05

Wouldn't a capacitor across the relay contact fix the contact arcing/welding problem?.

UndermineBriarEverglade - 4-11-2024 at 09:08

Thanks Gawain. I will try a contactor. I do have magnet wire, but apart from the relay damage I haven't had any detonation problems so I'm probably not going to change the load.

fx, I think it would cause more arcing when the contacts first close in favor of reducing arcing when the relay opens. I don't know if the problem is arcing on open or on close, but I suspect it's arcing on close that's the problem since the relay gets stuck closed when it fails. I also don't want to spend my microwave capacitor's energy charging another cap instead of exploding the wire. (And I don't want to explode an inadequately-rated filter cap either.)