Induction brass annealer redux
- Thread starter Gina1
- Start date
Are you using a relay between the induction board and PS, or are you trying to use the remote switching function of the PS? I found the remote switching function does not work to make the tank circuit resonate, and it hits low voltage/high current.
This is the one I ordered: https://www.jameco.com/webapp/wcs/s...Jmkp3o=&ddkey=https:StoreCatalogDrillDownView
Note - it's a 24v solenoid. You either need to add a 24v power supply (Gina1 went through spec'ing this part, and a dual 12/24v power supply earlier in the thread, somewhere around page 28-30, I think?), or... you can run this solenoid at 48v off the main power supply as long as the duty cycle is less than 25%, which it definitely should be. This is currently my plan (the 48v route). Will post back here how it works out - the rest of my parts should arrive in the next couple of days...
Blew the induction board today
Heard a pop and found this:
View attachment 1033056
Quality of these things is not great. My first one blew immediately, this one made 1000+ Rounds.
What are you using for the power relay (PS to induction PCB). DPST contactor relay or SSR) ??
Reason I'm asking, is we had one builder try to use a single pole-single throw relay, to switch power to the inductor PCB. Something about arcing across the relay contacts, when the relay opened after an anneal. I see from your pictorial that you are using a SPST SSR. I'm wondering if this back surge is not blowing your PCB.
Just a thought....
I've run 1,000's of cases through, with no problems with the inductor PCB.
Gina
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I guess I could try two of them. I’ve run 200-300 cases at a time without a problem before. I Checked the temp with an infrared thermometer and it wasn’t that hot. I’ve got an extra so it’s easy enough to try.
Thanks. Yes, I have the Packard two pole relay between the board and the power supply. I pulled the MOS FETs off the board this evening and used a voltmeter in "diode" test mode to test them and they seem OK. I can buy a set for cheap so I will re-solder/replace them anyway. Like you hinted earlier, I'm starting to suspect the power supply is somehow the culprit. I'm debating upon purchasing the RSP-750-48 in order to have the current control. Then just re-wire the whole assembly again. The most painful part is the wait for parts. No too bad if I get it to work, again.
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Yes, waiting is the hard part. If it is, the PS the 750-48 will give you a bit more power. Hopefully that is your problem, and you can get back to annealing.
BTW where are you located ?
Thanks, I'm in the south bay Los Angeles area.
I used the RSP-1000-48 hoping to have extra power headroom so the power supply didn't need to work so hard.
At this point, control is more important.
Last night I wondered if my two pole relay contactor is faulty somehow. Both poles have clean open and closed positions but I wonder if they are "off-timed". It seems unlikely but one never knows. The unit also worked fine without "voltage sense" feedback from the load for the several months it ran.
Hopefully I will look at it some more this weekend and if no resolution, order the power supply Monday. Then I'll match the configuration to most everyone's build to avoid confusion.
jthor
USAF Shooting Team
Got it! Though this solenoid just popped up! Figures I ask the question and then I find a decent 12VDC solenoid.
https://www.jameco.com/z/SH-T2551L-Solenoid-12V-Pull-Type-Solenoid-10-Watt_2196748.html
I don't think it is the relay contacts, since the coil pulls the the whole assy (both polls) at the same time,
I never used that voltage sense. Has worked for more than a year just as a regular PS.
Wish I could take a look at it, hands on. Sorry... I'm sure you will get it going again.
BTW how much current were you drawing when you annealed a case ? (when it was working)
Gina
I used that link to take a look at that solenoid. Unless the solenoid has a built in spring in the case, you may need to add a light weight spring to get the armature into the out position.Got it! Though this solenoid just popped up! Figures I ask the question and then I find a decent 12VDC solenoid.
https://www.jameco.com/z/SH-T2551L-Solenoid-12V-Pull-Type-Solenoid-10-Watt_2196748.html
Take a look at the video in the beginning of this thread. You can see the spring on the solenoid.
Good luck
Gina
Thanks for listening and all the help. I'm happy I found this design from all the contributors.
The latest update is that I pulled the power supply and ran it bare and it seems to not deliver voltage anymore without the resistor input control. It had previously worked that way when I first received it but now is not. It looks like it was the power supply all along explaining why everything else looked OK. What is confusing is why I was getting 40V output indicated (or voltage I chose from resistor control). I'm guessing (again) the unit would give me low current voltage but drop voltage when higher current demands started. GrocMax's guess the power supply tripping a safety is the "winning entry" for this problem (If I'm allowed to pick a winner). I'll test some more tomorrow (likely get no resolution from the PS) and just order a new power supply. New RSP-750-48 seem to run ~$180 at the best price. I'm not retired and I could shoot that value in ammo on a busy weekend so the price isn't too bad.
I used this seller on eBay. They have all sizes of power supplies for about 1/2 the cost. It shipped DHL so was here in a week.
https://m.ebay.com/sch/i.html?_from=R40&_nkw=totiwo+&_pgn=3
https://m.ebay.com/sch/i.html?_from=R40&_nkw=totiwo+&_pgn=3
Thanks Dskogman,
What was the seller's name? The link is dead because it may link to your personal login.
I found "20gtlion15". They are out of Taiwan.
Here is a link for info on the RSP-750
http://www.meanwellusa.com/webapp/product/search.aspx?prod=RSP-750
Looks like it has some really good information
Gina
http://www.meanwellusa.com/webapp/product/search.aspx?prod=RSP-750
Looks like it has some really good information
Gina
Welcome to the world of the flyback!
An inductor has a unique effect on some circuits. If a current is flowing through an inductor, and you disconnect the circuit, the inductor will try to maintain this current at all costs! What happens is that the flyback effect tries to maintain current by causing a huge flyback voltage.
So, if your relay is switching between two blocks, and either one has an inductor in series with the current flow, you will have a huge voltage transient soon as the contact is lost. This voltage starts an arc that will discharge the energy stored in the inductor and will sustain arching and current flow till the current drops the inductive energy below the voltage to maintain the arc. 'Course, by now your relay contacts are welded together, burnt away or a PC trace fuses open.
Most induction heater circuits have inductors in series with the power FETs so these inductors are probably the culprit. Many power supplies with built in current limit may have an inductor at the output also with minimal capacitance so the current limit circuit is the limiting factor, not the energy in the capacitor (which opposes any change in voltage such as a short circuit). You either must put in a series resistor to limit current (not a real good solution as it uses up power and will not protect till the arc forms). The other solution is to put a capacitor across the contacts that will buffer the flyback by absorbing the energy from the inductor in a somewhat controlled fashion. A current limiting resistor can be placed in series with the capacitor as well. Back in the analog days, engineers were well aware of this effect so relay coils usually had a series resistor-capacitor across them to suppress flyback from either frying the relay contacts or transistor driving the coil. As well as guarding against this problem across relay contacts or switch contacts.
An inductor has a unique effect on some circuits. If a current is flowing through an inductor, and you disconnect the circuit, the inductor will try to maintain this current at all costs! What happens is that the flyback effect tries to maintain current by causing a huge flyback voltage.
So, if your relay is switching between two blocks, and either one has an inductor in series with the current flow, you will have a huge voltage transient soon as the contact is lost. This voltage starts an arc that will discharge the energy stored in the inductor and will sustain arching and current flow till the current drops the inductive energy below the voltage to maintain the arc. 'Course, by now your relay contacts are welded together, burnt away or a PC trace fuses open.
Most induction heater circuits have inductors in series with the power FETs so these inductors are probably the culprit. Many power supplies with built in current limit may have an inductor at the output also with minimal capacitance so the current limit circuit is the limiting factor, not the energy in the capacitor (which opposes any change in voltage such as a short circuit). You either must put in a series resistor to limit current (not a real good solution as it uses up power and will not protect till the arc forms). The other solution is to put a capacitor across the contacts that will buffer the flyback by absorbing the energy from the inductor in a somewhat controlled fashion. A current limiting resistor can be placed in series with the capacitor as well. Back in the analog days, engineers were well aware of this effect so relay coils usually had a series resistor-capacitor across them to suppress flyback from either frying the relay contacts or transistor driving the coil. As well as guarding against this problem across relay contacts or switch contacts.
Hi dskogman. Sorry for the late reply. After looking at your board, you seem to have used one of the two boards I have used. This is the board with 4 MOS FET mounted to heat sinks and 8 capacitors, correct? (The other board has two MOS FETs and 6 capacitors). I noticed you didn't put a heat sink on the board (maybe removed it for photo). Whenever I ran the unit the board would heat up most around that region that you show as damaged. The MOS FETs and capacitors themselves would not heat up much but only on the board in that region you show. In my testing, I would would run a half dozen cases, quickly shut it down and feel the board for hot and warm areas. This region seemed to get hot enough to make me try to cool it down. I ended up thermal epoxy bonding large heat sinks over the region you show. I used some 15lb fishing line between the bondline to make sure the bonded metal heat sink would not short any traces on the board.Blew the induction board today
Heard a pop and found this:
View attachment 1033056
Quality of these things is not great. My first one blew immediately, this one made 1000+ Rounds.
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Thanks but I did remove them for the picture. I used some kind of "thermal tape" but maybe I need a better conducting bond. I am going to add another SSR so it's a double pole like Gina recommended.
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