07-09-2013, 02:06 PM
Thanks for your observations Gary and Alan.
1n fact after about 200 RPM, the calculator ceases to count - I guess because it can't cope with keystrokes above that speed, and wasn't designed for such a need,. but I don't envisage the winder going at anything like that speed (12,000 turns per hour). True, a reed switch could be used and would only need a small neodymium magnet to operate it, but in terms of reliability, a 'tally counter' operated by a cam as shown in the first video above would be the simplest method, albeit it would make a clatter at high revs, as evidenced in the video. I tried a tally counter on my hand operated coil winder, but the spring was too strong so I had to dismantle the counter and take turns off the spring. ((Tally counters only about a fiver).
Really, a turns counter for this application is a needless non-essential distraction - the number of turns is irrelevant - what matters is that the resistance of the finished coil is 2,000 Ohms or thereabouts. I'm away from home at present, but as I recall, the 500g reel of 38SWG wire I've bought is 2,700 Ohms. When the bobbin is full, I'll check the resistance and either add or remove turns as required. I only fitted the counter as it was easy enough to do, and I thought it would be interesting to know how many turns the coil eventually takes.
As I see it, a turns counter is more relevant when winding RF coils, and the inductance, rather than the resistance, is important. In such cases, a turns counter is helpful for repeatability.
For an electronic counter, I think the most reliable option would be a digital frequency counter module (not much more than a tenner from Asia Engineer et al), triggered by a slotted disc and opto-interrupter, interfaced with the counter module. A disc with 60 slots will convert the display into RPM rather than frequency in Hz. (Thus, 1 rev would give 60 pulses). I built such an arrangement to display RPM of my woodworking lathe based on an article in Model Engineering Mag which forum member Ted, Ex-2Base, kindly passed to me. However, I couldn't devise a convenient way of mounting the slotted disc on the lathe, so the project stalled. As with the coil winder, it's a non-essential requirement as my lathe has eight fixed speeds and I know what they are and what speed the lathe needs to run at for a given size of object.
Interesting enough, but of little relevance to the task in hand - winding a field coil.
1n fact after about 200 RPM, the calculator ceases to count - I guess because it can't cope with keystrokes above that speed, and wasn't designed for such a need,. but I don't envisage the winder going at anything like that speed (12,000 turns per hour). True, a reed switch could be used and would only need a small neodymium magnet to operate it, but in terms of reliability, a 'tally counter' operated by a cam as shown in the first video above would be the simplest method, albeit it would make a clatter at high revs, as evidenced in the video. I tried a tally counter on my hand operated coil winder, but the spring was too strong so I had to dismantle the counter and take turns off the spring. ((Tally counters only about a fiver).
Really, a turns counter for this application is a needless non-essential distraction - the number of turns is irrelevant - what matters is that the resistance of the finished coil is 2,000 Ohms or thereabouts. I'm away from home at present, but as I recall, the 500g reel of 38SWG wire I've bought is 2,700 Ohms. When the bobbin is full, I'll check the resistance and either add or remove turns as required. I only fitted the counter as it was easy enough to do, and I thought it would be interesting to know how many turns the coil eventually takes.
As I see it, a turns counter is more relevant when winding RF coils, and the inductance, rather than the resistance, is important. In such cases, a turns counter is helpful for repeatability.
For an electronic counter, I think the most reliable option would be a digital frequency counter module (not much more than a tenner from Asia Engineer et al), triggered by a slotted disc and opto-interrupter, interfaced with the counter module. A disc with 60 slots will convert the display into RPM rather than frequency in Hz. (Thus, 1 rev would give 60 pulses). I built such an arrangement to display RPM of my woodworking lathe based on an article in Model Engineering Mag which forum member Ted, Ex-2Base, kindly passed to me. However, I couldn't devise a convenient way of mounting the slotted disc on the lathe, so the project stalled. As with the coil winder, it's a non-essential requirement as my lathe has eight fixed speeds and I know what they are and what speed the lathe needs to run at for a given size of object.
Interesting enough, but of little relevance to the task in hand - winding a field coil.
Regards, David.
BVWS Member.
G-QRP Club Member 1339.
'I'm in my own little world, but I'm happy, and they know me here'
BVWS Member.
G-QRP Club Member 1339.
'I'm in my own little world, but I'm happy, and they know me here'
