Hi guys, I'm currently devouring all info to see how I can make my own battery spot welder.
Got a couple of questions if anyone can shed some light:
1) kdog says above that a higher activation voltage might help turn the SSR on quicker, but I thought these SSR's are opto-coupled: the control input just turns a light on which triggers the output relay? I was hoping to drive the input with a 5V micro arduino...
According to the SSR-40DA specs (which most people seem to be using), available at:
http://www.photosensor.com.tw/Solid%20State%20Relay/Single%20Phase%20Solid%20State%20Relay%20(DC%20to%20AC%20SSR)(UL)/SSR-40DA-H.htm
the min voltage needed for a signal is 2.4V, and the trigger current is 7.5mA at 12V, so at 5V for the same power it should be 18mA, which is less than the 40mA max draw for a Micro Arduino signal pin.
Shouldn't this be ok? What am I missing?
2) The response time on the SSR seems to be on the order of 10ms, what sort of timings are needed for welding 0.15mm battery tab, will 10ms be too long and burn the nickel plates too much?
3) I am currently debating between building a MOT welder and a car lead-acid battery welder. I've already sourced a couple of MOTs. It seems to me the MOT is easier to build, as the SSR will handle the switching and the Arduino is easily programmable. But it seems recently everyone is talking about battery-based welders. Any pros and cons? It would seem to me that the battery-based welders are more complex and more expensive to build, with the 6x mosfets and schottky diodes etc. And at the end of the day the MOT welder will be more powerful and can be used for welding thicker pieces if the pulse width is lengthened, whereas a battery cannot handle long pulses and there is a risk of being damaged by the short circuit. The only downside with the MOT is dealing with high voltages from the mains power?
I noticed that flangefrog already built an MOT welder years ago, but decided to build a battery-based one recently? flangefrog, can you give some insight?
4) If going the car battery route, why can't we use something analagous like the SSR-100DD which will switch a DC output instead of building the 6x mosfet circuit that everyone seems to use? (Ok, I guess we can't because we are dealing with 500-800Amps....
)
Thanks in advance for any replies
Got a couple of questions if anyone can shed some light:
1) kdog says above that a higher activation voltage might help turn the SSR on quicker, but I thought these SSR's are opto-coupled: the control input just turns a light on which triggers the output relay? I was hoping to drive the input with a 5V micro arduino...
According to the SSR-40DA specs (which most people seem to be using), available at:
http://www.photosensor.com.tw/Solid%20State%20Relay/Single%20Phase%20Solid%20State%20Relay%20(DC%20to%20AC%20SSR)(UL)/SSR-40DA-H.htm
the min voltage needed for a signal is 2.4V, and the trigger current is 7.5mA at 12V, so at 5V for the same power it should be 18mA, which is less than the 40mA max draw for a Micro Arduino signal pin.
Shouldn't this be ok? What am I missing?
2) The response time on the SSR seems to be on the order of 10ms, what sort of timings are needed for welding 0.15mm battery tab, will 10ms be too long and burn the nickel plates too much?
3) I am currently debating between building a MOT welder and a car lead-acid battery welder. I've already sourced a couple of MOTs. It seems to me the MOT is easier to build, as the SSR will handle the switching and the Arduino is easily programmable. But it seems recently everyone is talking about battery-based welders. Any pros and cons? It would seem to me that the battery-based welders are more complex and more expensive to build, with the 6x mosfets and schottky diodes etc. And at the end of the day the MOT welder will be more powerful and can be used for welding thicker pieces if the pulse width is lengthened, whereas a battery cannot handle long pulses and there is a risk of being damaged by the short circuit. The only downside with the MOT is dealing with high voltages from the mains power?
I noticed that flangefrog already built an MOT welder years ago, but decided to build a battery-based one recently? flangefrog, can you give some insight?
4) If going the car battery route, why can't we use something analagous like the SSR-100DD which will switch a DC output instead of building the 6x mosfet circuit that everyone seems to use? (Ok, I guess we can't because we are dealing with 500-800Amps....
) Thanks in advance for any replies
